Quite obviously, you’re going to need node.js and mongodb installed. I recommend downloading and installing from the node.js website and following the instructions. I will note that this tutorial covers 0.6.7 so if you come across this post a year from now the API might have changed significantly since then. You will also need mongodb installed, you can download it here. If you use Ubuntu (or some other Debian derivative) you should consider installing from their apt repository. OSX? No problem, you can also install it via homebrew or macports.