The information you really need depends on whether you have previously developed using entity beans before.
If you have, then you should take a look at http://xdoclet.sourceforge.net, which will tell you exactly which tags (both generic ejb and jboss-specific) to use to get the elements you need in your deployment descriptors.
If you haven't used entity beans before, then you really need to understand how they work before you try and accelerate the process with JBoss IDE's XDoclet support. If you don't have the basic knowledge, it will be frustrating and unpleasant. In my opinion, the best reference out there for learning EJB is O'Reilly's Enterprise JavaBeans, 3rd Edition
By Richard Monson-Haefel
3rd Edition September 2001
You can get it through www.amazon.com or www.bookpool.com (usually cheaper)