Either online or download the app onto your phone and have it ready as you walk in.
They should send you an email with your ticket, otherwise I'd use my phone with the QR code
Amc App or you can have the credit card or order number and print them there.
When you get the theater you just ran the QR code and it will print your tickets
On the app
If you can't from your phone open your computer, or just show your open app to the theater attendaant the barcoden
When you buy your tickets it should give you the option to print IF you're using a computer (a printer icon should pop up somewhere) IF by phone i'd recommend screenshots so they can scan the code on your phone. Usually they ask for an email too and they'll send you your tickets via email, in form of a PDF or it will just be embedded in the email.
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