Trouble getting started

I can confirm your installation section is apparently not idiot proof. I'm running Firefox and have just installed the Stylish add-on. I tried Stylish once before but gave up having not found a theme I could like. Yours looks tempting but I'm lost on how to use it. I made a git clone of your repo and then took a WAG by clicking on the S > Manage styles ... > Install from URLS ... > entered full path to my clone's styl/dark.styl with a prefix of "file://". I gave it a name of "Solarized-Everything" and then exactly nothing seemed different. :-(

I removed that attempt in the Stylish manager and retried with sites/all-sites.styl and still nothing.

Where did I go wrong?