Where should i manually edit ? Please let me know

Where should i add  the CSS code below?.product-dynamic-checkout {display: none; visibility: hidden;} 

I would need  to disable the I agree with terms and conditions button and enable  the Buy it now button . Also remove the Categories and Tags piece on the product page. Below  is the URL to my store: https://www.zonkefarms.com/products/whole-chicken-...

I am having  the same problem - My store link is https://zifad.myshopify.com/ and my email address is vcapital2015@gmail.comThank you and look forward to hearing from you.Best,