For the full Quantum feature list, see the parent README.md.
Download or clone the whole firmware and navigate to the keyboard/pegasushoof folder. Once your dev env is setup, you'll be able to type make to generate your .hex - you can then use the Teensy Loader to program your .hex file.
Depending on which keymap you would like to use, you will have to compile slightly differently.
To build all keymaps, simply run make, the .hex files will end up in the top directory.
Several version of keymap are available in advance but you are recommended to define your favorite layout yourself. To define your own keymap create file named <name>/keymap.c in the keymaps folder, and see keymap document (you can find in top README.md) and existent keymap files.
To build the firmware binary hex file with a keymap just enter the keymap directory and type make:
$ cd keymaps/default
$ make