Normally our customers would use Vendio checkout, and the buyer would pay through PayPal in that way. You can enable Vendio checkout by going to "My Account" --> "Post Sale Management".
If you just want the PayPal pay now button in your Winning Bidder Notifications, and no checkout, then you would need to manually enter the HTML code for the PayPal button. You add it to your WBNs by going to "My Account" --> "Post Sale Management" --> then manually enter the HTML code into your "Winning Bidder Notification (WBN) Email".
