So you have access to the the wiki and now the question might be what do I do?
Here is a short tour around the site and so pointers on how you might become more active.
If you are new to google sites, there are two videos to help you learn how to work in google sites:
1) overview of google sites and
2) learn how to use this site-- they are both short and watching these videos will help you become an expert.
You can use the sandbox to get comfortable with editing the pages.