how to install via npm code example

Example 1: install latest npm

npm install npm@latest -g

Example 2: install an npm package

npm install package-name

To save as a dependency:
npm install package-name --save

Example 3: what is npm install

npm install module-name
npm i module-name
puts module-name package (js library file) 
into node_modules folder
so you can require it in node app