The power button on your cell phone is either a distinct key, or a shared function key. Phones that have a shared function button almost always have the Power and End Call functions on the same key. You press and release the key to end a call or return to the main menu, and press and hold the key to turn the phone off or on. Phones with full QWERTY keyboards sometimes have more than one power button. One button is on the outside of the phone, and the other is on the keyboard.
Locate the power button on the phone. Some phones say "PWR" or "POWER" while others have a power symbol. Look for a circle with a vertical line through the top.
Press and hold the button for a few seconds.
Release the button when the phone turns on or off.