Its best if You go through documencation: http://docs.jboss.org/jbpm/v5.2/userguide/
and than if you need more info on specific functions or classes help yourself with api docs: http://docs.jboss.org/jbpm/v5.2/javadocs/
If this is not enough than come back and ask questions. User guild is realy good and after reading WHOLE you get a good high and middle level view on how to use engine, guvnor and jbpm console. This will be a good start to further reading or asking questions.