Oh, I’m on a mac :D
For this challenge in particular, you’ll want two things, both installable through Homebrew. From a terminal, type:
brew install nasm qemu
This will give you both nasm (the assembler) and QEMU (a reasonable PC emulator). There are other options for both, but that’s what I used when making Snakelight!
Other nice emulators you might like to test with are DOSBox (available from brew install dosbox) or 86Box.