You can add the photos using one of two methods.
1. You can use ebay's Revise listing feature to change the listing, i.e. modify the Description section to add (cut and paste) the photos or that text (HTML code) from your Activa saved listing. This one needs a little finess to understand how to get the HTML code off Auctiva and exactly where/how to insert or replace code, but can usually achieve best results with complex templates and image presentations.
2. Use the Auctiva Add Images feature for active listings. http://www.auctiva.com/free-auction-software-help/help.aspx#add-images
I generally use and prefer method #1, and really haven't played much with #2.