Once you're logged in, a grey floating 'Tool' menu at the right hand side of the screen enables access to all the main 'Content Pages' for editing. (Note: Some pages, such as the site info etc. are locked)
Like most Wikis, the site doesn't use HTML for formatting (security reasons etc). The special syntax is very comprehensive (a guide can be found), but has quite a steep 'learning curve', so, in front of the original there's now a built-in and relatively simple as the default system - which makes basic editing much easier.
There's a 'Switch Editor' button at the top of the page which allows logged-in users to switch between the two systems at any time.
Registered users can also navigate back to previous versions of the page to undo recent changes.
The best way to create a new page is to use the 'Create a new article' link (above left) That way you can easily choose which category to create the new page in.
If you'd like to experiment, use the '' pages, where you can create anything as a test.
In a departure from normal 'wiki' pages, it's possible to add an which appears at the top of the page. The idea is to distinguish exceptionally enigmatic and important items from minor ones - see top of this page as an example.
(You need to use the original 'Syntax Editor' to do this.)
At present, only users who have been given 'Editor' status can upload images.