You run it right from your browser: on every notebook, there is a run button, or you can click the run button on any cell and all cells up to and including that one will run. You can also embed the notebook in any web page using the script tag visible when you click the share button. And if you have our you create a web page that has the notebook embedded in it, you can run that I your browser from your desktop. Finally, the notebook code is all available from github, with instructions.
Note that there there's the notebook site, which shows instructions and your list of notebooks; and then there's the notebook itself, embedded in it or in any other Web page.