hi Luis Victor,
you can use the drools-guvnor to edit the evaluation example process.
you can refer to this http://docs.jboss.org/jbpm/v5.3/userguide/ch.installer.html#d0e559 and this http://people.redhat.com/kverlaen/jbpm-installer-guvnor.5.2.swf on how to upload the sample process to guvnor. and then you can just edit it in guvnor.
another good reference is this video http://vimeo.com/26126678