Can I use Apple Pay to make a payment on a website using my Mac?
To pay on the web in Safari on your Mac, select Apple Pay and complete the payment using either your iPhone or Apple Watch. On Mac models with Touch ID, pay using Touch ID.
Your Mac needs to be signed in to the same iCloud account as the iPhone or Apple Watch and have Bluetooth enabled on your Mac.
At the check out
a) The default card can be changed by clicking the button next to the default card and selecting a new credit or debit card from any iPhone or Apple Watch which is nearby and signed into the same iCloud account.
b) If you need to, enter your billing, shipping and contact information. Apple Pay will store that information on your iPhone, so you won’t need to enter it again.