1. Compile an i686-elf GCC and binutils following the instructions on this page:
   https://wiki.osdev.org/GCC_Cross-Compiler

2. Install yasm, or modify the makefile to use nasm if you prefer it

3. Run make in the source root

4. Run boot.img with some emulator, I use qemu:
   qemu-system-i386 boot.img
   You can use the x86_64 qemu, Bochs, VirtualBox or something else if you prefer