At the checkout, tap the Apple Pay button or choose Apple Pay as your payment method.
To pay with a different card, tap the Next button or the Expand Menu button next to your default card.
If necessary, enter your billing, delivery and contact information. Apple Pay stores that information so you won't need to enter it again.
Confirm the payment.
iPhone or iPad with Face ID: Double-click the side button, then use Face ID or your passcode.
iPhone or iPad without Face ID: Use Touch ID or your passcode.
Apple Watch: Double-click the side button.
Mac with Touch ID: Follow the prompts on the Touch Bar and place your finger on Touch ID. If Touch ID is off, tap the Apple Pay icon on the Touch Bar and follow the prompts on the screen.
Mac without Touch ID: Confirm the payment on your Bluetooth-connected iPhone or Apple Watch. Make sure you're signed in with the same Apple ID on all devices.