If you still don't have NodeJS installed, you must do it before start your epic project.
You can download NodeJS here.
Install RhapsodyJS CLI
To install RhapsodyJS CLI globally, you must run the command:
$ npm install rhapsody-cli --global
To generate a new RhapsodyJS app, you should go to the folder where your app folder will be, and then run:
$ rhapsody-cli new APP_NAME
This will generate the basic structure of your app
$ cd APP_NAME && npm install $ rhapsody-cli run
And then your app will be running in localhost:4242.