The simple answer is that you really can use Apple Pay at McDonald's. You cannot, however, use PayPal with Apple Pay because Apple Pay does not currently support it.
To use Apple Pay in-store, simply place your order and show the cashier with your iOS device, where you can then scan just on a contactless reader to pay.
Q&As about Apple Pay at McDonald's
If you're wondering if McDonald's accepts Apple Pay, the bellow might also answer all of your questions.
A large yellow M McDonald's logo is displayed against a wooden wall.
Yes, Apple Pay is accepted at all McDonald's locations. McDonald's, for example, was an early adopter of Apple Pay and has been accepting it since 2014.
Yes, Apple Pay is accepted at McDonald's drive-thru. Apple Pay is also supported in the McDonald's app.
Yes, Apple Pay is accepted at McDonald's. This payment method is accepted in the store, the drive-thru, and on their app.