there's a few different ways to go about doing it (putting code for it in your template, is one way, for example)
easiest way is to turn it on to be automatically inserted at bottom of all listings by auctiva.
link to do this is:
http://www.auctiva.com/account/preference.aspx check the box for "Enable Auctiva Store Window" in the Account Preferences section of the page and then click "update account preferences"
to find the link in future:
click Store tab
click Store Window link
then you will see text that will say one of two things:
Your Store Window is currently: Enabled. Click here to go to your account preferences page to disable it.
or
Your Store Window is currently: Disabled. Click here to go to your account preferences page to enable it.
click the link where it says "click here"
After you do this, will want to customize it. link to customize is
http://www.auctiva.com/stores/editstorewindow.aspx to find it, it's the Store Tab, then Store Window, then Edit Store Window
If you want it in a specific place in your template, then you need to create a custom template and insert the HTML tag for the Store Window. I dont know the tag offhand, but it's in the templates section of site (and Donna, lisa, and some of the others here can also point the way to putting tag in template)