How to edit an existing wiki page
The simplest way is letting the box 'Doubleclick editing' marked in your Settings when you log in. That way, all you have to do to start editing is double clicking anywhere the page you want to modify! When you double click the page, a text editor will open. Once you've finished your changes, go to to the bottom of the page, where you'll find three options, "store" (to save the new page with the changes you've made), "Preview" (to see how it all looks before committing, very useful to learn about formatting), and "Cancel", to discard the changes.
Remember, however, that you have to be logged in before you can make any change to a wiki page. If you find a page you want to modify but you are not logged in atm, here's an easy way to do it:
1: copy (ctrl+c) the URL of the page you're at and that you want to modify
2: press the Login/Register icon at the top of the page, type your username and password, and log in
3: once you're logged in, paste back (ctrl+v) that URL in your browser, to return to your desired page, but this time logged in and ready to modify.
Other methods
In addition to double clicking, if you're logged in, the pages will show an 'edit' link at the bottom of the page.
