Congratulations. I think it's very appropriate to have an entry for "IP address" in tinWiki, for several reasons. You have made an important improvement of tinWiki with your contribution. I want to offer two minor style comments: the normal headers (with two equal signs on either side) get underlined automatically, so one doesn't need to put in the underline manually; and, adding an asterisk at the beginning of each line in a list (for example a list of links) will make it a bullet list. These are just minor style issues, though.
To answer your question, then: To place an article in a category, simply place a link to that category anywhere in the wiki code; you see, categorizations will automatically appear at the bottom of the article, no matter where in the wiki code you place the link. Still, it's common to place the category codes at the very end. A list of categories is here. Example of categorization:
[[category:Conspiracy Theories]]
Keep up the good work.
Optimist
