How to apply theme to only specific store pages

So, this site is not only a store. I have already created a child theme for the site and only want to adapt the FrameMarket to fit with the child theme. How does this happen? I have made a child theme folder for FrameMarket, but haven't added anything into it yet. I am assuming the WPMU child theme work the same, where you only create the elements you want to change inside the child folder? Or can I just add the elements to my main child theme folder?

Haven't activated the theme, yet, since it changes the whole site.

Thank you!