Clone the repository recursively. Angular, Flat-UI, and angularFire are submodules of this repository. This makes it extremely easy to get update versions of all of them.
CD into the angular/ directory and Grunt it. This will build all necessary files into the angular/build directory. Now when you Grunt the root directory, it will copy down files to the app. This will also start up the local server, the same as grunt serve will.
In the controllers file, app/js/controllers.js you will need to set the ref variable for your Firebase application.