example on how to use

Ok so you give instructions and show how to install but not how to use.

I've got a an web app (not javascript) that has a template language and builds html files from templates and uses some css. How do I run it?

This isn't very clear:

usage: purifycss <css> <content> [option ...]

options:
 --min                Minify CSS
 --out [filepath]     Filepath to write purified css to
 --info               Logs info on how much css was removed

 -h, --help           Prints help (this message) and exits

Report bugs to: https://github.com/purifycss/purifycss/issues

What's css? a single file? multiple files? Can I point it at a webserver?

Same with content, am I meant to point it at a downloaded file built from the templates?

An example of running it manually without using grunt or gulp would be nice.