Hi ebr-sales,
If you have the Auctiva Checkout setting in your account enabled, any listings you post through your Auctiva account will automatically be processed through the Auctiva Checkout system. The Auctiva Checkout system is integrated with eBay's system such that your buyers would actually reach Auctiva Checkout by clicking the same "Pay Now" button on the auction pages that they are used to using.
You don't have to make any changes in your eBay or Paypal accounts for the Auctiva Checkout system to function, but you might want to set up your combined shipping and insurance rules within eBay to make sure your transactions are treated as desired when your buyers purchase more than one item for you at the same time if you have not done so already.
If you have any other questions regarding your Auctiva account, please feel free to contact our customer support team using the form on the following page of our site:
http://www.auctiva.com/help/requesthelp.aspx-Mike