This documentation is only for the desktop app. It will be updated soon for the mobile apps as well. Thanks for your patience.
Add Icon to APIs
You can add icons for APIs. It is optional. But, definitely makes your Radar listing look good.
Click the Pencil icon of an API on the listing page, select Next. In the Icon URL textbox, input an image URL. That's all. You will see an icon left to the name of your API. Make sure the image is square.