need to install zip code shipping box

WP Help. Please tell me how to install the wp ultra simple shopping cart. I have most of it done except when I go to settings , usage , then option #2 there is no mention of how to install a Zip code box so that customers can enter same an get the price of shipping for product. There is 4-5 choices for a shipping ap but none of them say anything about how to get this zip code box that every co. needs.