Here are the steps if you are trying to use Oracle with jbpm console:
http://community.jboss.org/people/bpmn2user/blog/2011/02/26/orcale-integration-with-jbpm5
If you are using a stand alone example and persisting using API you can follow the following example. You can uncomment the Oracle configurations in persistence.xml etc and use your host details.
http://community.jboss.org/people/bpmn2user/blog/2011/02/26/orcale-integration-with-jbpm5