WooCommerce theme integration issues

Looked through a lot of the woocommerce help files but couldn’t find what I was looking for–thought I’d check here.

I just installed woocommerce and am using a theme (Omega) which isn’t super compatible. It’s only selling one product on one page though, so I’m hoping it isn’t that big of a deal.

The width of the woocommerce checkout page is far too wide for my content div when there are items in the cart (and the fields are all misaligned etc). I can’t figure out which files I’d need to child theme in order to edit the css for it. Here is a link:

https://www.howtogetintograduateschool.com/checkout/

I’m new at this so apologies!