Below are the requirements which I found on the PopShops site. This may not be all, but it's a start.
You need to have your own website in order to use PopShops. Websites need to be hosted (unless you have your own servers), and all hosts are not created equal. If you want to use some of our more dynamic features (like AutoFeed and dynamic pages using Search), we recommend finding a host that supports PHP and uses cURL. For most hosts this is the default, but if you run into issues with the PHP code not working, check with your host to see if cURL is supported.
Make sure that the host you choose offers you unlimited domain hosting and reliable customer support. (Most hosts offer a trial period. We suggest taking advantage of that trial and contacting customer support.) Dreamhost has good customer support and an easy-to-use control panel.