From what I understand you should be able to just enable PayPal and eBay puts it on the EOA page regardless. However there is a setting you can check off in Vendio preferences that will enable it for both Vendio and eBay Checkouts. Please go to Global Preferences (located in your My Account section) and select the radio button under the section for PayPal:
"Include the PayPal Checkout button and logo in my listing (Required when using PayPal Immediate Payment, Buyer Financing Options or eBay Checkout Redirect)"
