Node.js can be easily installed by visiting the official Node website and accessing the Downloads section at http://nodejs.org/download/.
Once there, be sure to download the correct version depending on your OS and CPU (32 bit or 64 bit).
To determine which version of Node you want to download, you first need to determine your processor type: 32 or 64 bit. You can do this by executing the following command from a terminal:
$ sysctl hw | grep 64bit hw.cpu64bit_capable: 1
If you get 1 in the response, then you are running a 64-bit CPU. If the response is 0, then you are running the 32-bit version. Fortunately, there is a universal installer specifically for Mac available from the Node website; however, if you wanted to download the binary, at least now you know which to get.
Once the download is complete, double-click on the .pkg file, which will launch the Node installer (as shown in the following screenshot):
