Develop? You just have to see the source code and follow it to *try* as we do, to understand it. I'd suggest you (i did that last week) to start with the folder process.example and ther websample.par, then jbpm.identify, src/java.examples/org.jbpm.websale, src/java.webapp (mbeans) and of course JSF and all the content of the folder websale.war. Hope it helps...
sorry, i meant "jbpm.war" in C:\jbpm-xxx\jbpm\src\resources