Finding/creating user css

I see many references to “user css” in the articles here for solving specific problems (such as this one that I’m trying to solve “filter oversized smilies” )

But I can’t find anything in the file tree named “user.css” and I’m not sure where to put it or create it. I also don’t see any references to “user css” in the theme section of the wiki.

@fox when you refer to “user css” what exactly do you mean?

Preferences > Theme > Customize

you’re not on twitter, don’t @ me directly unless there’s a reason.

4 weeks probation hoping you would either learn some manners or fuck off of my forum.