AngelsBlue is asking the right questions. I will expand a little. You are very close. First create your Seller Details here: Profiles tab>Seller Details
The last screen is where you name your seller details and save.
Once this is done, on your listing creation page, select your template and set up your picture configuration.Then select your named/saved Seller Details in the drop down menu to the right of the "Select Template" link. The template (in Preview) should now show Description, Payment, Shipping, etc. and pictures.
This Seller Details "set" you have created (which doe's not include Description and pictures) will stay in memory. You can create as many "sets" as you wish, selectable in the aforementioned drop down menu. Each time you create a new listing Auctiva combines your selected pictures,new title, new description, and selected Seller Details "set", onto your chosen template. This is independent of the other information on your listing eg. starting price, shipping details, checkout options, etc. It's a very flexible system and works great once you get the hang of it.