where to run npm install from code example

Example 1: how to install any package in node.js

#how to install any specific package in nodejs Application
# Syntex
npm install packagename

# example:
npm install express
npm i express

#if you install globally then type 
npm install express -g

Example 2: install an npm package

npm install package-name

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