how do i install npm code example

Example 1: install latest npm

npm install npm@latest -g

Example 2: intall npm

npm install -g npm

Example 3: install npm

curl -sL https://deb.nodesource.com/setup_6.x | sudo bash -
curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
sudo apt-get install -y nodejs
sudo apt-get install -y npm

Example 4: 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