Board Thread:Support Requests - Getting Started/@comment-26842327-20150606184931/@comment-1038387-20150606191125

Did you want Harry Potter (Movies) to be added to the page? In that case, you did it backwards: you added the page to the category, rather than the category to the page.

If you go to Harry Potter (Movies), you'll see a bar at the bottom (above the comments). It has "Add Category". Click that. In the input line that appears, add "Movie Characters", press enter and OK. If you do that, you've categorized the page.