A sample Meteor scaffold has been created for you in /home/nitrous/code/example. It is the equivalent to running the following:
meteor create example
You can start the server by running ~/code/example/start-app from the command line. Once it is running, you can use the preview menu to view the application in a new tab. Opening the ~/code/example/start-app file is a good way of finding out how to get your own Meteor application running.
Feel free to remove the ~/code/example directory if you no longer need it.