could you attach you bpmn2 file? It looks like it's missing name of the work item and thus cannot find the work item handler for it, so process instance is aborted. From console point of view you only need to register work item handler that will perform the work for defined work item (task). They are referenced by name - on one side in bpmn2 and on the other on ksession. To register handlers on ksession in console you need to use session.template file as mentioned in the link above in jbpm docs.
HTH