To add or edit information on a page in the wiki, go to that page and just hit the "edit" tab at the top. You'll be able to change the information you want. It's a good idea to add a note as to what you've changed/added in the "Log message" box. Then hit the "Submit" button at the bottom.

To make a new page in the wiki, go to the page where you want to add a new page link to, and click on the link "add child page" at the bottom. Give the page a sensible title and choose where the page best belongs by selecting a page from the drop down list. Add in your information and hit the "Submit" button at the bottom.