To add a new category to a page you can click the Category button at the bottom of the page and type in the name you'd like your category to be called.
A full list of existing categories can be found at Special:Categories.
Pages in category "Browse"
“ This page lists all of the other pages on the wiki. Please don't post a link on this page...
List of Pages
“ Units | Special Units | Weapons | Equipment Aircraft | Armoured Vehicle | Warship | Spacecraft ...