Instruction 1:
1. First of all, take off the phone's back cover and remove the battery.
2. Wait a few seconds and reassemble the phone. Lastly, press the Power button to turn it on.
Instruction 2:
1. First, press-hold Power button. When a list of options appear, select Power Off. Confirm by tapping Ok.
2. Press the Power button again, this time to turn the phone back on. Done!