To turn off your mounted tablet, hold the red power button on the back of the tablet. You will see a mini menu pop up in the top-right corner of the screen. Choose "Power off" to turn off the tablet.
You can turn off the tablet and the bike all at once by simply unplugging the bike from the wall socket.
The tablet will also go to sleep automatically after a set time. To adjust this time, go to the More page of the app, select Preferences, and select Screen Sleep Timeout.
You can also press the red power button on the back of the tablet to instantly put it to sleep.