Thread:Sannse/@comment-39264654-20190512150328/@comment-8-20190513171939

You need to go to the page that you want to add a category to, and click edit. There is a icon with three bars on the toolbar (next to the "cancel" button). Click that and you will get a menu that includes "categories". Click that to get the categories dialog box.

Let me know if you get stuck!