Hi Mare3369,
You can go to the tab at the top that says "Store" and then click on "Edit Store Window". Here you can choose what type of window you want and where you want it located...above or below item description (mine is set to go below item description as well). Then just save your changes and you should be all set!
Hope that helps...let us know if you still have troubles.
Marcia
My Ebay Store