The first step to becoming a wiki editor is to request a wiki account. Wiki accounts allow users to edit pages, and it is different from a forum account. To request a wiki account just use our regular contact form. Forest will create your account in a day or two, at which time you will be able to edit wiki pages.
While you are waiting for the account, you can watch the following video, recorded while this new wiki was being built, and also read ahead in the tutorial.