If you are modeling an user task you can focus on three porperties:
DataInputSet - create/modify the data inputs of your task
DataOutputSet - create/modify the data outputs of your task
Assignments - create/modify data assignments (map existing process vars/data objects to task data inputs, and map data outputs to existing process vars, data objects) ...
The DataInputSet and DataOutputSet editors I think are self explanatory (let me know if you need more info on those)
Let's say you have process variables
firstName
lastName
and your user task defines data input firstnameIn and data output lastnameOut
in the assignments editor you would first map your process var to the data input:
https://community.jboss.org/servlet/JiveServlet/downloadImage/2-821112-20906/450-232/Screen+Shot+2013-06-03+at+6.51.21+PM.png
and for the data ouput mapping you can do:
https://community.jboss.org/servlet/JiveServlet/downloadImage/2-821112-20908/450-219/Screen+Shot+2013-06-03+at+6.53.25+PM.png
that should be pretty much it, not that the actual values of data outputs are typially entered by your hunam actors during the execution of the process via forms, your custom workitem handler in case of doman specific task node etc.
HTH
