How do I pay for something on Amazon using Apple Cash/card/pay?

This may help you understand how you can use Apple Pay to pay for purchases in Amazon in the countries where Apple Pay is available.

Amazon says, "Amazon Payment Services fully supports Apple Pay. You can offer your customers a seamless payment process via their Apple mobile device."

Digital wallets - Amazon Payment Services

Start here at http://www.Amazon.com

Next:

Finally:

Then enter your card’s information.