Go to the agent's tab and click on an agent you have created

Once inside your agent panel you will have 4 tabs to choose from - Configuration, Chat Interface, Analytics, Cached Answers, and Safeguards. Click Chat Interface.

The Chat Interface tab is where you can customize the look, feel, and design on your agent. There are two categories of customization you can choose from Popup window and button and Chat window.

To customize, simply adjust the toggles, sliders, and buttons available to you.