How to edit Single.php file for framemarket/gridmarket


I am a bit confused on how to edit/style the single post pages (as well as the archive, and 404 pages) I have been using gridmarket as a guide for all of the style changes, however the single.php file is only in the framemarket directory. I tried making a copy of it and putting it in the gridmarket directory, but that didnt seem to work.

I know youre not supposed to make edits directly to the framemarket theme, so I am wondering how I can edit the files that only show up there (like single, and archive ect)