How do I create a Wiki for my site?
It's simple; just activate the Wiki module and start adding content. Check out this quick guide to the feature": http://www.groups-corp.com/wiki/item/using-the-wiki-module
How do I rename or delete categories in the Wiki?
You can manage the wiki module/page by going to your admin panel (Tools) and then Pages. Click Administer next to your Wiki page. You will be able to manage the wiki and have the option to edit/delete categories along with the option to add new categories.