Just create a new discussion in our ProM Forum. Also join the ProM mailing lists: http://listserver.tue.nl/prom-users and/or http://listserver.tue.nl/prom-developers.
The three steps to get started quickly:
Petia Wohed has written a very good webtutorial on Workflow and Petri nets. It is available here.
Also see the World of Petri Nets and the book Modeling Business Processes:
A Petri Net-Oriented Approach by Wil van der Aalst and Christian Stahl.