How use resource element as file xml in workflow ?

Good afternoon,

In my workflow, I set an attribute parameter with type Resource Element and the value of attribute is a file xml.

And i got a problem to use file xml in my workflow, i would like to use theses informations from file xml to store in variable..

Example : in file xml, i put some information about number VLAN ID, and in my script task, i would like know how is use with myvariable.portgroup[0].spec.vlanId ?

Best Regards.