How I can change my theme generated with remote theme starter

Hi guys,
I am really beginner in Jekyll. I`ve created my blog in github pages with Minimal Mistakes remote theme starter. I clone MM starter repo, changed some configs in yml files and pushed in my repo.
It works nice but I would like to have thumbnails neard posts headers. How can I change theme?
In my repo I cannot see any html/css files.

I user minimal-mistakes remote_theme:
remote_theme: “mmistakes/minimal-mistakes”
minimal_mistakes_skin: “air” # “air”, “aqua”, “contrast”, “dark”, “dirt”, “neon”, “mint”, “plum”, “sunrise”

I solved it by replacing remote theme with local one.