Open the Wallet app.
Tap the "+" sign in the upper-right corner.
Enter your card's security code to add your Debit affiliated with your iTunes account or select "Add a different card," and use your iPhone camera to scan the card information.
Open the Apple Watch app on your iPhone.
Tap "Wallet & Apple Pay" and select "Add Debit Card "
Enter your card's security code to add your credit or debit card affiliated with your iTunes account Or, select "Add a different card," and use your iPhone camera to scan the card information.
*For a list of compatible Apple Pay devices, see support.apple.com/km207105
Pay easily, and securely with Apple Pay.
Paying in stores
To pay with Face ID, double-click the side button, glance at your screen, then hold iPhone near the reader. For Touch ID, hold your iPhone near the reader with your finger on Touch ID. On Apple Watch, double-click the side button and hold Apple Watch up to the reader.
Paying in apps and on websites
To pay in apps and on websites in Safari on your iPhone and iPad, select Apple Pay at checkout and complete the payment using Face ID or Touch ID.
To pay on websites in Safari on your Mac, select Apple Pay and complete the payment using your iPhone or Apple Watch. On MacBook Pro, pay using Touch ID on the Touch Bar.