Css help for Squarespace (always show additional info on products)

I am setting up a webshop in Europe, and squarespace has to many flaws for both european law and tax etc.. So i have decided to keep my page in squarespace and add a button to each product linkind directly to Shopify. The problem is that the only way i can add HTML on each product is in the additonal tab. An this doesnt show automatically. It just pops up in a light box, see:

http://www.roam.dk/parachilna/aballs-m-pe

Can you help me program some css that will enable additional information to be shown under the product description on all products i have?

And what will this cost approx?

Im using Squarespace template SUPPLY.

Best ragards Lasse Astorp