WP e-Commerce Predictive Search – where to tag for search

Hi, I’m pretty inexperienced and I’m having trouble getting the WP e-Commerce Predictive Search Lite plug-in to “find” anything on my site. I am unclear what it is searching for – page or post names, image names, tags, etc. Everything I enter comes up with a search not found message. I’m happy to pay for the Pro plugin, just wanted to figure out what the free version could do. Can someone help me get started?
Many thanks!
Laura