My 2014 Sunseeker came with it activated. We didn't have to do anything special. We started using the MH the day after we purchased it less than 3 weeks ago and are still on that trip. A couple of days ago our free trial ended. I suppose I should see if we didn't get the full trial.
EDIT: Bad info. I just got off the phone with SiriusXM. They had a free trial for everyone for 3 weeks that just ended. That's what we were listening to. I'm going to go to the SiriusXM.com site and see if my radio ESN is eligible for any free trial. I will report the answer here. My dealer didn't know.