Setting Up LS2

I just installed this plugin on my development site as it seems to be exactly what I am looking for. We use TLC’s LS2 catalog located at tlc.hayslibrary.org. I am able to get items to display if I input the ISBNs manually but I would really prefer to use the web service call. For the life of me, I cannot figure out what I should be putting in the Request URL field. I am trying with a saved search that I have and have tried both the catalog url with the search identifiers, and the url for the RSS feed. Any guidance would be appreciated.