You need to download the Node.js pre-built installer and install it to your computer. You can get the latest version of the Node.js here - https://nodejs.org/en/download/. NPM is distributed with Node.js - which means that when you download Node.js, you automatically get NPM installed on your computer.
To check if you have Node.js installed, run this command in your Terminal/CMD:
To confirm that you have npm installed you can run this command in your Terminal/CMD: