In order to get this to run you will need to install the npm dependencies and setup the connection to your WordPress.com blog.
Clone the repository, then run npm install from the installed directory.
To connect to your WordPress.com blog, edit config.js and set siteId to either the numerical ID of your blog or the full domain, such as snelladventures.wordpress.com. Note that mapped domains on WordPress.com are also valid, such as snelladventures.com.
When these two steps are finished, start the live-editing environment in your browser with npm start.
You should now be able to open up localhost:4001 in your browser and start to mess with the code. As you make changes, you should notice almost immediate updates in the browser. If something doesn't reload properly, simply refresh the browser.