To connect your digital drum kit to your computer with midi or bluetooth, you click on settings wich can be found in the drum sheet page or rhythm game page.
Click on "Change your input controls" and select "midi input". Here you will find your midi device. If you want to use bluetooth select "Connect to bluetooth device".
You can choose to use the default input settings, wich will work in most cases. But you can also setup your own. Use the easy setup method or the advanced to control the game with different midi notes.