The Node.js installers and distributers can be found on its official website http://nodejs.org/. The installation procedure differs, depending on the operating system.
On Windows, two MSI based installers are provided at http://nodejs.org/download/, one for a 32-bit OS, and another for a 64-bit. To install Node.js on Windows, simply download and execute the installer.
For Mac OS X, a
pkg installer is available at the same location; downloading and running the PKG file will allow you to install Node.js with the Apple installer.
On Linux, the installation procedure depends on the distribution. Instructions for many popular distributions are available on the node wiki at https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager ...