Do you mean the item specifics?
I asked a similar question a few days ago.
It seems that a link appears for some categories on the new listing page that enables you to enter the item specifics - but in my experience it doesn't appear for all categories (as it does on eBay) - so I am currently doing what you are doing and revising my listing on eBay after posting from Auctiva.
Maybe someone from the Auctiva team could clarify this for us?