To pay with iPhone and Face ID, double press the button in the right side of your device, glance at your screen, then hold the iPhone near the reader.
To pay with iPhone and Touch ID, hold your iPhone near the reader and rest your finger on the Touch ID pad
To pay with iPhone device passcode, hold your iPhone near the reader and enter your device passcode.
To pay with your Apple Watch, while wearing your Apple Watch double press the side button and hold the display up to the contactless reader to authorise a payment.
It is important to note that the Apple Watch NFC feature has to be enabled before Apple Pay will work. When you strap your Apple Watch to your wrist you will be prompted to enter the device passcode. Once entered, this will enable Apple Pay. When your watch is removed from your wrist, the Wrist Detect will detect that skin contact has been lost and Apple Pay and NFC are deactivated.