you will find every street corner, has a big sign said, discount ticket booth.
these tickets are after market multiday tickets, meaning they are activated by someone else, when you buy them, you do not need to pay upfront, they hold a charge on your credit card, when you return the tickets, you just pay for whatever days you used.
most theme parks are finger printed now days, since these tickets are after market, so its already got someone else's finger print on it. the ticket booth people will tell you, at the gate, tell the gate person, these are group tickets, you happen just got the wrong ones from the tour director.
when you at the gate, pick a young gate person, mostlikely they don't care, because these all well know secrets, you just re-finger print them as you enter.
I done many times, never ran into problems, but you doing it at your risk of embrassing yourself...lol...