Summarize this article:

To buy on eBay using PayPal you must first win a bid on eBay or use the eBay "Buy Now" option that allows you to purchase eBay items immediately without going through the bidding process. You will know that the item is ready for payment when you see the "Pay Now" button appear next to it on the "Bids/Offers" page that can be found through the "My eBay" link at the top of most eBay pages.  If you want to change the shipping address, you can use the "Change shipping address" link to provide a new shipping address. If everything looks correct, you should press the "Continue" button to move ahead.

Summary:
Get the item ready for payment. Press the "Pay Now" button next to the item that you want to make the payment for. Confirm your shipping address. Verify the payment amount and details such as shipping cost and tax as well as the total cost. Choose PayPal as the method for making the payment. Use the login information of the PayPal account that you had linked to log in to PayPal through eBay. Reconfirm the details of the order such as the shipping address and payment amount. Press the "Confirm Your Payment" button to finalize the PayPal payment process.