Hi realdealrings,
To update your custom eBay store categories within your Auctiva account, please go to Auctiva -> My Account(Tab) -> Ebay Settings, and click the "Update Store Categories from eBay" link.
Once you have done this, there will be two pull down menus on the Auctiva lister page, direclty below the cateogry field, from which you can specify up to two custom eBay store catogories for each item.
-Mike