If you want to display a chat button in your customer portal, follow these steps:
Create a chat button and copy its integration code
To create a chat button please follow this guide. Once you create a chat button, LiveAgent generates a chat button code (see Step 10 of the guide mentioned above). Copy the code, so you can use it in the next step.
Insert the chat button code into customer portal
In the agent panel, navigate to Customer portal > Settings > General Configuration - Change.
In the customer portal settings navigate to the Tracking codes section and insert the chat button code into the Before </BODY> field. Don't forget to hit the Save button.
That's it. Your chat button is now displayed on your customer portal: