Great plugin for integrating jboss and jbuilder. I've actually talked to a developer on this, and they actually have some people at borland helping on this. Should support jbuilder 8 soon too.
The way I do this is to create a datasource for the module so I can see the tables, and I map the table/fields from the EJB Designer tool in the bean. Keep in mind, any datasource configuration in the EJB Module Datasource tool will not work on JBoss and the voyager plugin. You will then need to add a datasource and a datasource mapping from the Entity Bean property editor (open the module in the project pane, and click on the entity bean. This will open the property tool (lots of tabs) for that bean. The latest version of the Voyager tool (in CVS) is suppossed to have a CMP editor tab.
Hope this helps!