The rules for basic page editing are fairly simple--start each line without spaces and put a blank line between paragraphs. There are more Text Formatting Rules? for lists and other specialized text, if you want to do that. You can edit the WikiSandbox page if you want to try things out in a way that won't affect any of the pages on this site.
To create references to other pages, run capitalized words together to make a WikiWord page title. This automatically creates a hyperlink. Make titles for NewSubjects, even if you don't have anything to say about them. Maybe someone will come along and fill out a page for the new link.
A page's full name is GroupName.PageTitle, such as Main.HomePage. To refer to a page in the current group, write its PageTitle. To refer to a page in another group, write its full name.
If the page you want to make has no natural WikiWord title (for example it might be one word) use [[double brackets]] to create a link.