To run the application your Spotify account needs to have the developer flag set. You can find out how to activate the developer flag here.

Clone this repository in your Spotify workspace directory. If you haven't got a Spotify directory, read about where to create it here. Cloning will create a subfolder called musision.

You can access the application (restart the Spotify desktop client if you have not done so) by typing in spotify:app:musision in the search field. Read more about this in the Spotify Developer Guidelines.