Remove "leave a reply" text, twenty twelve child theme

Hi all,

I was creating my child theme in MAMP and all was well but when I uploaded my child theme to my site the “leave a reply” box appeared on single posts; see link:

https://www.lyzajheyden.com/category/designlayoutgraphic-designillustration/

Previously I created no php file to handle this and would like suggestions. I’m getting a bit confused by the forums and want to know if I should edit a child theme single, comment, etc php file. If you could be as specific as possible with the steps and code I would greatly appreciate it.

Many thanks!