From the NT Firearms Council website under Back Country Hunting:

Juniors or interstate visitors participating by invitation of the permitted hunter do not apply for and get a permit themselves - they are listed as a nominee on the permitted hunter's permit application.

All Permit Applicants, including Nominees, must have completed the BCH accreditation course and be a current member of a BCH (Parks & Wildlife) Approved Hunting Organisation. There are three such AHOs - SSAA, Australian Deer Association and NT Field & Game.