if you got your phone from bby, target or sprint, they will come with the phone, tmo att and verizon have to submit it on samsung's promo page. for att at least, you can use the receipt that comes in the box. it's what i used for my note 5 and it seemed to work fine.
just got mine today after going b/t home and work 4 times. went home for lunch, left, literally just missed the fedex driver (phone didn't buzz for some reason) so they left a door tag, ran back from work to try to catch him, got door tag, called fedex and asked if they could send him back, went back to work, got a call saying he's there, went back, got phone.
i didn't want to set it up at work so i just pulled the IMEI and MAC ID from it so i could submit the gear vr claim, and now here i am, with 2.75hrs to go and being totally unproductive.