Fix Woocommerce USPS integration

I have a woocommerce site and a plugin for usps integration but it is not working like I need it to, and I need urgent help. It wants to add up the weight of each item in the shopping cart instead of grouping them together as if it were going in one package. I want the end user if they have multiple items to have them quoted as if it were going in a certain size envelope or box. You have to have knowledge of the USPS plug-in and how it calculates prices according to weight/box size etc.