You can find the installers on Node.js download page. Normally, Node.js recommends two versions of Node, the LTS version (long term support) and the current version (latest release). If you are new to Node, just go for the LTS and then click the
Macintosh Installer button to download the package.
If you want to find other NodeJS releases, go here, choose your release then click download. From the download page, look for a file with extension
Once you downloaded the file (with extension
.pkg ofcourse), double click it to install. The installer packed with
npm, by default, the package will install both but you can customize which one to install by clicking the
customize button in the
Installation Type step. Other than that, just follow the installation instructions, it's pretty straightforward.
terminal (if you don't know how to open your terminal, look at this wikihow). In the terminal type
node --version then enter. Your terminal will look like this if Node is installed:
$ node --version v7.2.1
v7.2.1 is your Node.js version, if you receive the message
command not found: node instead of that, then it's mean there is a problem with your installation.