I just installed it on localhost. I just downloaded the "grav core + admin plugin" zip file (https://github.com/getgrav/grav/releases/download/1.0.8/grav-admin-v1.0.8.zip), unzipped it to a folder in XAMPP, and navigated to that page. Entered a username, password, email, and role, and that was it.
Installing new plugins is as simple as clicking the "Add" link at the top of the plugins page. (Same thing for themes.)
That is an awesome CMS. Thanks for bringing it to my attention!