If you want to contribute by improving the pages here, things aren't much more difficult. Follow the edit link, and type away in the edit box. Linefeeds aren't required except to separate paragraphs. To generate a link to a page at this site, use WikiNames. When you're done hit save.
Should one of the WikiNames refer to a page that doesn't exist yet, a "?" link will appear next to the name. Following this link lets you create the page. In other words, to create a new page you must first refer to it on some existing page.
It doesn't have to get more complicated than that unless you want to apply styling to your text or make links to something other than the pages here. Several characters have special meaning when used in a certain way. You can find out more about that by looking at WikiFormattingExamples.
For other tips, see WikiTricks and WikiHelp.