Cant’s find my wp-content/themes/tarski/styles/ directory…

This is probably something really simple I just have hardly any idea what I am doing.

I have a self-hosted wordpress blog and am running the tarski theme. I wanted to change the navbar but I don’t know how. It’s telling me to add a new style versus changing the original, and to go to my “wp-content/themes/tarski/styles/” directory but I don’t know where that is. All that I have on my actual computer is the wp-content with the classic and default theme folders in it.

What am I missing here?