When I went to the "new server wizard" I can't find the category for JBoss AS.
When I clicked "Download new server adapter" I don't get any JBoss AS adapter in the list.
Install the most recent JBoss Tools.
Go to Help > Install New Software.
Set Work with to the following URL depending on Eclipse version:
In the results, make sure that you've Group items by catagory checked and then select Web and Java EE development somewhere near the bottom.
Next, etc, Finish.
This will get you the JBoss-provided AS and EAP server plugins, along with several easing JSF development plugins, such as EL autocompletion.