React Hello World using command prompt

In this video the steps I have followed are:
1.= Download nodeJS and install it
2.= install create-react-app globally with node package manager(npm)
i.e. npm install -g create-react-app
3.= run the previously installed package in chosen directory
i.e. create-react-app my-app
4.= Navigate to newly created directory and start script
i.e. cd my-app/
npm start
5.= change app.js file according to print Hello World