Hi,
You'll find the Seller Details Profile in the Profiles tab section of Auctiva. The fill-out page is tabbed with the section headers used by the template. If you leave one blank, it won't fil-in that section. The Seller Details (by name) is then selected in the one-page lister to incorporate in building the listing.
You don't have to use Seller Details. You could simply build a template and add the info, minus the Seller Details tags. However, they do speed use of the templates, when you use many.
I would highly recommend the tutorials at the HELP link top of page to get you going.
Danno