Apple Pay allows you to store your payment information in a digital wallet that you can use to pay a regular debit card, for example. It is most useful with cash registers that allow you to pull out your phone instead of the wallet, but it also works on Macs when you shop online.
Apple Pay works seamlessly on newer Touch Bar Macs, however, if you have an On an older Mac, you need an iPhone or an Apple Watch for Touch ID authentication. In addition, Apple Pay currently works only in Safari, which could change in the future.
Setting up Apple Pay on your Mac
First, you need to enable Apple Pay in Safari. Open Safari Preferences, go to the Privacy tab, and select the "Allow sites to set up Apple Pay" check box.
You should have been asked to set up Apple Pay You must first set up your Mac, but if you did not add or need to change your card, you can do so at any time by opening your system preferences and click on the option "Wallet and Apple Pay". 
Add new maps, remove maps, change your default map, change your billing and delivery address, and view your recent transactions.
To add a new map, just click the + button below:
An attempt is made to automatically read your map information from the camera. This is a nice feature, but if that does not work, you can enter it manually.  If you have an older Mac
If you do not have a Touchbar Mac, you can not set up Apple Pay unless you have a Mac e iPhone. You'll need to add your card to your phone and then enable the "Allow payments on the Mac" option from the Wallet and Apple Pay settings on your phone.
This allows you to make Apple Pay purchases from your Mac, but you need to pull out or watch your phone to authenticate with Touch ID. Slightly less seamless, but at least compatible.
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