Unfortunately, there is no way to use PayPal directly on Amazon. There are, however, a couple of workarounds:
1. Get a PayPal debit card. All you have to do is link your bank account and another credit or debit card to your Pay Pal account. Once you have done that, you can then apply for a PayPal Debit Mastercard. This card can be used just like any other debit card to make purchases at stores or to withdraw money from an ATM. You can use it when you go through the Amazon checkout just like you would any other debit card. The only difference is that the funds will be taken out of your PayPal account. You can apply for a debit card for your PayPal account here:
2. Buy a gift card. There are countless online stores that sell Amazon gift cards. Many of these stores accept PayPal as a payment option. You could use your PayPal account to buy yourself an Amazon gift card, and then spend the gift card on Amazon purchases.  Although it is a two-step process, it is one way to use PayPal to buy items on Amazon.
Here's a video that shows you how to go about adding your PayPal Debit Mastercard to your Amazon account so that you can use it as a payment method during checkout:
Hopefully these ideas help!