To turn the phone on, press and hold the Power/Lock key until the screen lights up.
To turn the phone off, press and hold the Power/Lock key.
Tap Power off.
Tap POWER OFF.
If you are unable to turn your phone on, plug the phone into a power source for 15 minutes, then try again.
If you are unable to power your device off or if it becomes unresponsive, press and hold the Power/Lock and Volume Up keys for 10 seconds, until the device reboots.