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"
“ Hey, welcome to the Eldarya Wiki, Afterimageh. Thanks so much for your contribution to Nevra! To...
“ This category contains hidden categories. Unlike normal categories, these are not displayed at...