Fix Wordpress/Spreadshirt integration issue

I created a t-shirt shop in [login to view URL] and wanted to configure a frontend on my own domain. I bought the domain, installed Wordpress, bought a theme on [login to view URL] and a plugin to integrate Wordpress with Spreadshirt, so the client can add to cart on the main site an go to [login to view URL] only to checkout. Plugin works fine on default Wordpress theme but not with the theme I bought. I want to have that fixed so my Wordpress will be fully integrated with my Spreadshirt shop and have a good looking also. Please don't apply if you are not very well experienced with any of Wordpress, PHP or Javascript skills.