How do you use Apple Pay on Amazon

You don't. Amazon does not accept Apple Pay. You need to add your payment method to your account with them, and then they will use that payment method for any purchases you make.

Here’s what Rufus told me just now.

So I called customer support and asked a rep. They said no they don’t. I asked if many people call about it. She said she’s not allowed to say. That right there tells me something.

I googled it, and result show they do not accept Apple Pay.

Some 3rd party vendors on Amazon might, but Amazon themselves do not. And no, Rufus declines to answer whether they accept Apple Pay or not.