Integrating Shopify Buy Button with Custom Categories

Site URL: https://www.bostonterriersofboston.com/shop1

I want to integrate products onto my Squarespace site using the shopify buy button but I want to organize things into categories so people can find what they're looking for easily.  I tried using a shop page in squarespace but I am using a print on demand service and need shopify for shipping and taxes.  I have a few different categories and would really like to have everything organized.