Help:Contents
Create new articles by going into an existing article which should be linked to your article. Then put a double bracket around the title of the article you're creating, like this [[Title of My Article]]. Then save the page. Now click on the red link for Title of My Article and you will go to the new page you have created. Edit away and save it.
Following are some Wiki Help pages to setup
This is the same software that runs Wikipedia. You can learn most of what you need about editing articles there.
Sandbox -- Just a place to mess around with trying to create and save pages.
Wikimedia
StyleSheet and page layout http://www.mediawiki.org/wiki/Manual:Skinning