Getting started with editing / contributing
To start editing / contributing here, first click on "Log in / Create Account" in the top right. Make a new account - it's as simple as choosing a username and a password for yourself.
Then, at the section on the page that you want to edit / add to, click on [Edit] that will appear on the right side of the section's title. Alternately you can hit 'Edit' on the top to edit the whole page.
See this guide for tips on how to edit: http://en.wikipedia.org/wiki/Wikipedia:Quick_guide