You can pay for your ticket by card on the seller’s website. Within 3 hours after payment, you’ll get your ticket at the email address you specified in the booking form. If you didn’t receive it, check your Spam folder and make sure there were no mistakes in the email address. If you still can’t find it, read the article: I didn’t receive my ticket. What should I do?
You don’t have to print out your itinerary receipt. It’s only really there so that you don’t forget your flight details. The airline staff will only require your travel document to find you in the booking system and check you in if you haven’t already checked in online. They’ll give you your boarding pass, which you’ll need to board the plane.