Hi Mary.
Is there something specific we can help you with before you decide to leave? It's a wonderful, helpful community here, and Auctiva's support is pretty wonderful themselves. We're happy to help where we can! You'll find listings go so much more smoothly with Auctiva, once you learn the ropes.
Should you still decide to leave, here's the link with instructions. If you have questions about anything, please just ask.
http://www.auctiva.com/free-auction-software-help/help.aspx#close-account