One of the great new features in macOS Sierra is Apple Pay on the web in Safari. To use Apple Pay on your Mac you will need to sign into iCloud and have an iOS Device, also signed into iCloud, with a supported Credit card from a supported card issuer. When checking out on a site that supports Apple Pay, using the Safari browser, you can check out with just a touch thanks with the help of your iOS device. This makes purchasing items on your Mac simple and easy.
The new 2016 13 inch and 15 inch MacBook Pro includes Touch ID and Apple Pay. This is a welcome addition and an exciting feature. The out of the box experience is to walk through the setup assistant, on your new MacBook Pro, which now includes setting up Touch ID and Apple Pay. Making purchases with Apple Pay will be even easier because you can leverage the Touch ID built into your Mac without the need of an iOS device.
Something to consider. When setting up a second (or supplemental) user on your Mac, you will be able to setup Touch ID but you will not be able to setup Apple Pay IF another user already has it setup. In the event a second, third, fourth, etc user wants to leverage Apple Pay they can use Apple Pay on the web in Safari.
https://support.apple.com/en-us/HT204506
https://support.apple.com/en-us/HT201239
https://support.apple.com/en-us/HT205583
https://support.apple.com/en-us/HT204916
https://support.apple.com/en-us/KM207105