To add a new page to Wiki, all you have to do is come up with a meaningful title, capitalize all the words and StringThemTogetherLikeThis. Wiki automagically recognizes it as a hyperlink. Alternatively, you can put anything into [brackets].
Then you can go ahead and ClickTheQuestionMark at the end of your new hyperlink, and the Wiki will give you a window for making the new page.
If you wish to add documents with complex markup to the Wiki, you might be better off providing a URL to it than trying to add the text of the document here, like so:
PhpWiki project homepage: 
http://phpwiki.sourceforge.net/
The Wiki does not support most HTML tags, only the simpliest. See 
Help:TextFormattingRules.
<tags>They will just render like text.</tags> Wiki is meant to be as
simple as possible to encourage use.
Note that there is a feature that your system administrator can enable to allow embedded HTML, but there are security risks involved.