There are two different ways to use PayPal.
One is when you DO NOT have an account with them - in this case you enter your Credit Card info to make a payment.
Two is when you DO have an account with them - in this case you pay using your PayPal account, which is linked to a bank account and/or credit cards.
CJSIStrickland *seems* to indicate he has a paypal account, and added his amex gift card to his paypal account. I checked and American Express is one of the options when you want to add a credit card to your paypal account, but I don't know if it's possible to use an American Express card when you DON'T have a paypal account.