The FAQs Tab comprises only one panel:

It shows a list of all FAQ questions to be associated associated to the opened topic.

 Adding a question to a Topic

Simply drag a question from the FAQs component and drop it into the FAQs window. Check the Drag and Drop section for details. 

Deleting a question from a Topic

All you need to do is to select / highlight the question to be removed. This will reveal the Delete button, on which you click to engage the deletion process.