You might start here http://www.jboss.org/developer, you might use the "Get started" link on top of this page :)
Regarding JBoss 6.1.0, at the moment there are two different versions,
the community edition 6.1.0 is outdated and you should use JBoss AS7.1 or WildFly (the server is renamed)
If you download an EAP6.1* this might be ok. You can find several discussions in the forms regarding the differences between the EAP(supported) version and the community.