Hi Sadiroveski,
have you try to refer to this guide http://docs.jboss.org/jbpm/v5.3/userguide/ch.installer.html#d0e597 ?
about the DB, yes you can configure two DBs in your MySQL Database.
about building the DB tables, The db tables should be generated automatically when you have properly set all the persistence.xml and start the jboss AS.
I haven't do setup for MySQL yet, but the guide link above should have enough information about it.
I just tried to change the DB to MS SQL Server and can get everything run well now: https://community.jboss.org/wiki/SetUpJBPM53ToUseMSSQLServer2008