NodeJS can be downloaded here.
Alternatively you can install NodeJS through your operating system packager manager.
An excellent way to manage your NodeJS installation and be able to work with multiple version is to go through NVM.
Yarn is a package manager for your code. It allows you to use and share code with other developers from around the world. Yarn does this quickly, securely, and reliably so you don’t ever have to worry.
Instructions on how to install Yarn can be found here