There's more than one way to install Node, but we think the following instructions provide the best user experience.
We recommend installing Node and Watchman using Homebrew: http://brew.sh/ Install Homebrew, then run the following command in a Terminal:
brew install node
We recommend installing Node using Chocolatey, a popular package manager for Windows: https://chocolatey.org/
Install Chocolatey, then open a Command Prompt as Administrator and run the following command:
choco install nodejs.install
Follow the installation instructions for your Linux distribution to install Node 6 or newer: https://nodejs.org/en/download/package-manager/