Well, there's a users guide
here.
I'll have to write one up, the basics are very simple though (simpler than formatting a post actually)
The uber basics though, after you log in, click on the edit tab to edit an existing page, or any edit button to edit any existing section. Formatting tools will be available to you at the top of the edit window.
To link to a page in the Wiki, surround the word or words with [[]]. Example, "[[Bront]] owns Bront.org" will show up as "
Bront owns Bront.org".
To create a new page, simply create a link to the new page you wish to create and then follow it, and you will be brought to the edit page.
Existing links will show up as normal links in your browser (Blue or Purple depending on if you've followed them), non-existent links will show up as Red.
A history of every saved edit is kept, so you can look over changes and even easily undo them.