Question: how to use american express prepaid gift card on amazon?
Answer: Go to Amazon.com: Gift Cards.
Click on "e-GIFT"
Choose any design you like, and click on it.
For balance, choose "Set my own" and type in the exact balance on the Amex card in dollars and cents. ... 
Set your own email address as the recipient.
Checkout, paying with the Amex gift card.