how to stop the add to cart button from taking you to the checkout page in squarespace, but have it open up the cart on the side and allow you to stay on the product page until your ready to check out via your cart. 

Are you using a custom template?

On my Squarespace site, it adds the product to the cart https://www.abzglobal.net/products/p/squarespace-71-70-custom-blog-numbered-pagination

Thank you!