Hi David,
The only way you can control what goes in your store window is by making items hidden. To do this, go to Auctiva -> Store(tab) -> Edit Items. Items that are made hidden will not be shown in your store window the next time it refreshes, which it does about every 2 hours.
There is no way to select specifically which items you'd like to be displayed. We're working on a system that will give users more control over this for our phase II site, which should be released later this year.
-Mike