A friendly guide to building your personalised ChatGPT assistant (custom GPT creation) in under 30 minutes

The Quick Essentials

Before we dive in, here’s what you need to know:

• You’ll need a ChatGPT Plus or Enterprise account (the paid version)
• Creating a custom GPT involves naming it, giving it a personality, uploading knowledge files, and enabling tools
• The entire process happens at chat.openai.com/gpts
• No coding required — just plain English instructions
• You can keep your GPT private, share it via link, or publish it in the GPT Store

Step 1: Getting Access

First things first, you need a ChatGPT Plus subscription:

1. Head over to chat.openai.com
2. Click “Upgrade to Plus” if you haven’t subscribed yet
3. Confirm your plan and payment (USD $20/month at the time of writing)

Once you’re all subscribed:

1. Navigate to: chat.openai.com/gpts
2. Click the black “Explore GPTs” button in the left menu
3. At the top right, click “Create”

Brilliant! You’re now in the GPT Builder interface where all the magic happens.

Step 2: Starting in “Create” Mode

You’ll see a chat interface asking: “What would you like to make?”

This is where you describe your GPT in plain language. For example:

“I’d like to create a friendly GPT that helps junior marketers in the UK write social media copy. It should use casual British English and understand cultural references from across the UK.”

The system will respond with follow-up questions like:

• What tone should it use?
• Should it browse the internet or run code?
• Will you upload any knowledge files?

Answer naturally and conversationally. The system builds a draft GPT based on your answers.

It may even recommend a name and an image:

Once the chat version feels roughly right, click “Configure” in the top bar to manually fine-tune everything.

Step 3: Configuring Your GPT

This is the control panel where you can edit every setting. Follow these steps:

3.1 — Name Your GPT

• In the Name field: give it a clear name like “Brit Copy Buddy”
• In Description: write what it does — “Helps junior UK marketers write scroll-stopping social copy in casual British English.”

3.2 — Write the Instructions

Scroll down to the Instructions box and type your behaviour settings. Think of this like a personality manual. If you followed the steps, then it may well already be filled in for you. This is where the magic happens, so make sure it truly reflects your purpose. Because it is so important, we created a separate guide for this which you can read here. For example:

This GPT is a friendly and culturally aware assistant designed to help junior marketers in the UK write engaging social media copy. It communicates in a casual, approachable tone using British English, including regionally familiar slang and references from across England, Scotland, Wales, and Northern Ireland. It provides clear, supportive guidance to help users improve their writing, offering creative suggestions while keeping brand voice and audience in mind. It can reference UK cultural events, holidays, humour, and idioms to make content feel local and relevant. It avoids Americanisms and ensures that grammar, spelling, and phrasing are aligned with UK standards. The assistant will ask for context when needed (e.g., target audience or platform), and will aim to keep things breezy, witty, and scroll-stopping.

3.3 — Add Conversation Starters

Under Conversation Starters, add 3–4 useful prompts users might click on:

• “Help me write a tweet for a UK skincare brand launch”
• “Can you make this Instagram caption sound more British?”
• “Draft some TikTok captions about a new meal deal”

This helps users jump straight in without typing from scratch.

Step 4: Adding Custom Knowledge (Optional but Recommended)

If you want the GPT to reference your own documents — like brand guidelines or FAQs — follow these steps:

1. Scroll to the Knowledge section
2. Drag and drop your files (accepted formats: .pdf, .txt, .csv, .md, .json)
3. Upload limit is around 20 files at present

Example: Upload a “Tone of Voice Guide.pdf” and your GPT will use it to match your brand style.

Important note: Your GPT can reference but not quote files word-for-word. It learns the content conceptually rather than memorising exact phrases.

We have created a step-by-step guide for the best way to structure your Knowledge files here.

Step 5: Enabling Tools

Now choose which abilities your GPT should have.

Scroll to Capabilities, and toggle the following:

• ✅ Web Browsing — useful for real-time info like news or trends
• ✅ Code Interpreter — for handling files, calculations, data plots
• ✅ Image Generation — if you want it to create pictures (e.g., Instagram ideas)
• ✅ File Uploads — lets users feed the GPT spreadsheets or PDFs

Select only what’s genuinely useful — too many tools can make your GPT’s responses confusing.

Step 6: Testing Your GPT Thoroughly

Before publishing, have a proper chat with your GPT.

Ask both straightforward and unusual questions to test:

• Does it maintain the right tone?
• Does it understand your uploaded files?
• Does it use tools properly (like making charts or browsing)?
• Does it clarify things when uncertain or guess incorrectly?

If anything feels off, go back to the Instructions and tweak your wording. Even changing one line can make a significant difference.

Step 7: Create New Action

This function allows you to turn your GPT into a powerful API-aware assistant that can fetch data, trigger services, or complete tasks — all from inside the chat.

This is an optional extra when creating a Custom GPT and is complicated enough to need its own guide, which you can read here.

If this is your first attempt at creating a Custom GPT, we suggest skipping this step for now and moving on to Step 8.

Step 8: Switch Off Training

You should always consider anything sensitive you share with any AI chatbot. However, its always a good idea to switch off the request to improve the AI models.

Step 9: Publishing Your GPT

At the bottom right, click the “Publish” button.

You’ll be asked to choose:

• Private — only visible to you
• Unlisted — only people with your link can access it
• Public — listed on the GPT Store for anyone to use

Give it a thumbnail image (upload one or use the auto-generated option), choose a category (e.g., Marketing, Productivity), and confirm.

Congratulations! Your GPT is now live and you can view it.

Final Tips for Success

• 🧹 Keep it focused — One GPT = one clear purpose
• 🪪 Use your brand voice — match the tone your users expect
• 🔁 Iterate regularly — update your files and instructions as you learn what works
• 💬 Share wisely — use private/unlisted first before going public

Happy GPT creating! With these steps, you’ll be up and running with your custom assistant in no time.

You may also find useful:

• How to Upload Knowledge into Your Custom GPT
• How to Use the “Create an Action” Feature in Custom GPTs
• Or try this playbook out now at ChatGPT by tapping here.

Your step-by-step guide to making a smarter GPT with your own documents.

Why Upload Your Own Knowledge?

Even the best GPT won’t really sound like you — or know your stuff — unless you teach it. That’s where knowledge uploads come in.

By uploading files (PDFs, DOCs, TXT, etc.), your GPT can:

• Answer questions based on your business material
• Speak in your tone and style
• Cut down on repetitive manual responses
• Act as a trained assistant, contract reviewer, customer explainer, or internal helpdesk

Think of it as giving your GPT “homework.” You hand it your documents, and it quietly studies them behind the scenes so it can sound smart in front of your users.

Why Upload Your Own Knowledge?

Even the best GPT won’t truly sound like you — or know your stuff — unless you teach it. That’s where knowledge uploads come in.

By uploading files (PDFs, DOCs, TXT, etc.), your GPT can:

• Answer questions based on your business material
• Speak in your tone and style
• Cut down on repetitive manual responses
• Act as a trained assistant, contract reviewer, customer explainer, or internal helpdesk

Think of it as giving your GPT “homework.” You hand it your documents, and it quietly studies them behind the scenes so it can sound smart in front of your users.

Step-by-Step: How to Upload Documents to a Custom GPT

Prerequisite: You’ve already created your Custom GPT (via https://chat.openai.com/gpts). You’re now ready to add your own knowledge base by uploading documents.

Step 1: Go to the GPT Builder
Go to https://chat.openai.com/gpts. Click on your Custom GPT and select “Edit GPT.”

Step 2: Find the “Knowledge” Section
In the left-hand menu, select “Knowledge” and click “Upload files.”

Step 3: Add Your Files
Drag and drop or browse to upload your documents. Supported formats include .pdf, .docx, .txt, .md, .csv. You can upload up to 20 files with a combined size of 512 MB. You can ask ChatGPT to help you assess and convert documents into these formats if you need to with this prompt:

I want to use this document inside a Custom GPT as part of its Knowledge section. Please assess the content and do the following:

Identify if this content is suitable to be uploaded directly (e.g. clear, clean, complete), or if it needs to be rewritten, summarised, or broken into smaller chunks.

If the formatting is poor (e.g. tables, layout issues, scanned PDF style), convert it into clean, text-based markdown or plain text format that preserves all meaning and structure.

Remove any unnecessary elements such as headers/footers, page numbers, duplicated content, or visual formatting that won’t translate well into plain text.

Structure the output into a clean, well-labelled text file that can be uploaded into the Knowledge section of a Custom GPT (i.e. .txt or .md format). Use clear section titles and bullet points where appropriate.

Keep all the important content, but make sure it’s optimised for retrieval by a GPT model. That means using simple, clear language and logical structure.

Name the output file appropriately (e.g. “2025_PricingOverview.txt” or “Legal_Terms_Guide.md”).

Please begin by assessing the suitability of the input and then output a clean, upload-ready version.

[Optional Tip (if you’re uploading a file):
Start with:]
“Please assess the uploaded file using the instructions below…” and paste the prompt afterward.

Step 4: Check the File List
You’ll see a list of your uploaded files. Use the trash icon to remove any if needed. You can update this list at any time.

Step 5: Save and Publish
Click “Save” or “Publish” to apply your changes. Your GPT can now access your uploaded documents to answer relevant prompts.

What Kind of Files Work Best?

Ideal Files:

• Cleanly written PDFs (guides, SOPs, FAQs)
• Contracts and legal templates
• Onboarding documents, pricing sheets
• Internal wikis (exported to .txt or .md)

Avoid These:

• Scanned documents with images
• Slides with only images or no speaker notes
• Encrypted or locked PDFs
• Files full of links without explanations

Tip: For web pages, copy-paste the content into a clean .txt or .md file.

How the GPT Uses This Info
Your GPT will search the uploaded documents in real time when a relevant prompt is given. It doesn’t memorise the content — it retrieves from it. It performs best when the material is clearly written and structured.

Watch Outs

1. No File Structuring = Confused GPT
   If you upload a single giant PDF with 50 topics and poor formatting, the GPT will struggle. Break it into smaller, well-labelled files.
2. Bad Formatting = Bad Responses
   If your file has unusual fonts, broken tables, or visual layouts (especially common in PDFs), the GPT may misread it. Clean formats like .txt, .docx, or markdown work best.
3. No Source Citations
   By default, GPT won’t say where the information came from. If this matters, add an instruction like: “Always mention which document you’re referencing.”
4. File Limit
   You can only upload 20 files per GPT. Curate carefully and consider trimming or combining related documents.

Curating the “Core Knowledge” for Best Results

Ask yourself:

1. What do I want this GPT to do? Only upload documents relevant to those tasks.
2. Will someone else use this? Include glossaries or context if needed.
3. Is this content clear and self-contained? If not, simplify or split into manageable chunks.

Example Use Cases:
LegalGPT: Upload contracts, clause trackers, fallback templates
SalesGPT: Upload pitch decks, product specs, objection-handling guides
HRGPT: Upload company policies, onboarding FAQs

Bonus Tip: Pair With System Instructions

After uploading, adjust your GPT’s instructions to reflect how it should use that knowledge. Example: “You are a helpful assistant trained specifically on SQREEM’s legal contracts and internal SOPs. Always answer using information from the uploaded documents. If unsure, say ‘I’m not certain — please check with legal.’” You can also use the “Prompt Starter” section to load reusable queries.

Updating Your Knowledge Files Later

Return to “Edit GPT > Knowledge” anytime to remove outdated files or upload new ones. Save to apply changes. Your GPT will instantly use the latest content.

Version Control and Multiple GPTs

You can create multiple GPTs with different document sets, or use file naming conventions to stay organised. Examples:
01_PricingOverview_Q1-2025.txt
02_TOS_Updated_April2025.docx
03_FAQ_InternalOnly.md

What To Do Next

Now that your GPT has your content, test it by asking:
“Summarise our latest pricing model”
“What’s our refund policy?”
“Write a client email using our onboarding flow”
“Check clause 7.3 in the uploaded SOW template”

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Turn your GPT into a powerful API-aware assistant that can fetch data, trigger services, or complete tasks — all from inside the chat.

TL;DR — What You Need To Know

• “Actions” let your custom GPT interact with external APIs — think booking systems, CRMs, weather lookups or internal databases
• You define the API, describe it with an OpenAPI schema, and explain when and how the GPT should use it
• Ideal for businesses that want to automate workflows inside ChatGPT — without needing full app builds
• Common use cases across Asia include: order lookups, stock checks, HR systems, and appointment scheduling
• This guide walks you through building, testing, and deploying your first Action step by step

What Is a GPT Action?

Actions allow your GPT to call an external API endpoint during a conversation. For example:

“Can you check the current air quality in Jakarta?”
→ GPT sends a request to an API you defined
→ Returns real-time AQI data into the chat

This means your GPT isn’t just a static assistant — it becomes a live, interactive tool that can “do” things.

Step 1: Set Up Your Custom GPT

Start as usual:

• Go to: https://chat.openai.com/gpts
• Click “Create”
• Fill out your GPT’s name, instructions, and tone as needed
• Switch to the Configure tab

Step 2: Prepare Your API

You’ll need an existing web API to connect. This could be:

• A public API (like OpenWeather, Google Calendar, etc.)
• A private internal API (e.g., inventory, HR systems, internal bots)
• A no-code tool like Zapier or Make, which exposes endpoints

Make sure:

• It supports HTTPS
• It accepts and returns JSON
• You have the API key (if it requires auth)

Example Use Case:
Check a user’s leave balance via an HR API.

Step 3: Write Your OpenAPI Schema

This is how GPT knows what your API does. You describe it using the OpenAPI 3.0 format — a structured YAML or JSON file.

Here’s a simple example for a GET request to check leave days:

yamlCopyEditopenapi: 3.0.0
info:
  title: HR API
  version: 1.0.0
paths:
  /leave-balance:
    get:
      summary: Check user's leave balance
      parameters:
        - in: query
          name: employee_id
          schema:
            type: string
          required: true
          description: ID of the employee
      responses:
        '200':
          description: Leave balance returned
          content:
            application/json:
              schema:
                type: object
                properties:
                  remaining_days:
                    type: integer

Paste this into an .yaml file or host it on a public URL (e.g., via GitHub Gist or a secure S3 bucket).

Step 4: Add the Action in GPT Builder

Back in the Configure tab:

1. Scroll to “Actions”
2. Click “Add Action”
3. Paste your API’s base URL
4. Paste or link to your OpenAPI schema
5. Add a description for GPT — e.g., “Use this action to check leave balances when users ask about time off”
6. Set authentication:
   • No auth
   • API key (via headers or query param)
   • OAuth (advanced)

Once added, test the schema using GPT’s built-in validator.

Step 5: Write GPT Instructions to Use the Action

Update your GPT’s Instructions to explicitly describe when to use the action.

Example:

When a user asks about leave days, use the HR API to check their balance. Ask for their employee ID first. Do not guess.

This ensures GPT won’t try to call the API unless it’s appropriate.

Step 6: Test the Action

Switch to Preview GPT and type:

“How many leave days do I have left?”
→ GPT should ask for your employee ID
→ Then call the action
→ Then return the result, e.g. “You have 12 leave days remaining.”

Watch for:

• Correct input formatting
• Unexpected errors or failed calls
• GPT failing to use the action when it should

Fix instructions or the schema if anything breaks.

Step 7: Publish and Maintain

Once you’re confident:

• Hit Publish
• Choose Private, Link or Public visibility
• Keep your API uptime in mind — if the endpoint is down, GPT won’t function properly
• Monitor logs and rate limits if it’s a high-traffic GPT

Real-World Examples from Asia

• Singapore travel agencies integrating visa APIs for instant eligibility checks
• Malaysian e-commerce startups checking stock or delivery status via GPT
• Indonesian HR tech firms adding internal policy lookups via GPTs
• Thai insurance brokers offering premium calculators through live API calls

The best part? You can connect more than one action — allowing your GPT to call several services like a digital command centre.

Security Note

Always hide API keys and use headers or environment variables for private services. GPTs do not store user data, but you are responsible for how your API handles it.

Avoid exposing endpoints with write access (like deleting records or submitting payments) unless fully secured and monitored.

Final Thoughts: ChatGPT as Your API Concierge

With Actions, GPTs are no longer just helpful assistants — they’re functional bridges into your real systems. In Asia, where lean automation is everything, this may be the most powerful GPT feature yet.

Whether you’re triggering a report, checking a shipment, or logging a support ticket — if there’s an API for it, GPT can now do it.

So the question becomes: what internal service would you automate first?

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