One of the major problems in jbpm5.1 is its lack of documentation. Or at least a central place to find it.
The first place you need to look at is the official documentation:
Kris Verlaenen's blog (jBPM5 lead):
Salaboy's Blog (Community lead ????):
I have a bunch of basic examples using JBPM5:
When you feel confortable enough, you can start playing with emergency-service application. It tries to be a blue-print implementation of jBPM5 and Drools: