Guest Relations is to the right of the turnstiles at the entrance.
I believe you should go to the designated Will Call window first. This would be one of the ticket booths (in the case of MK, at TTC, but there is at least some of the time a Will Call window at MK in the round building near the entrance). If that window is for some reason not open, then try Guest Relations.
You can also save some time filling out the form by
pre-registering...