Board Thread:Support Requests - Getting Started/@comment-24626194-20150505131203/@comment-1038387-20150514114746

StinkyTheAlpha wrote: Or more simply, go to the bottom(somewhere near the bottom)and you will see the categories. Click on the pencil to add categories, and click on the trash can to remove a category.

You can't actually remove categories via the bottom categories module. You have to edit the page.