Go to your terminal and there type
npm install express
Thats it congratulation you installed express from npm
Now you got one more file node-modules in your working directory
go to the project directory and run in command prompt
npm i express //i stands for install
//for installing globally
npm i express -g
npm install express
For npm users:
npm i express
For yarn users:
yarn add express
npm install express@4
npm install --save express mongoose ejs dotenv
yarn add express
yarn add --dev @types/express