Hi,
if you didn't change the default configuration you can access the H2 database with
http://localhost:8080/h2/h2
As JDBC URL you have to specify the H2 file on your disk, for example if you extracted the camunda distro to /home/camunda/jboss it would be
jdbc:h2:/home/camunda/jboss/camunda-h2-dbs/process-engine
The username and password is
If you changed the default H2 configuration or configured another database you have to adjust this values or use an external tool to access the database.
Cheers,
Sebastian