In this tutorial, you'll learn how to
• Turn on device
• Turn off device
• Lock and unlock device
Press and hold the Sleep/Wake button until the Apple logo displays.
Press and hold the Sleep/Wake button until the slider appears. Drag the Power slider to turn your iPhone completely off.
To unlock the device, press the Sleep/Wake button then press the Home button.  To lock the device, press the Sleep/Wake button.Â
Note: iPhone locks automatically if your device is idle for 30 seconds. To adjust the screen lock time, select the  Settings app > scroll to and select Display & Brightness > Auto-Lock > select the desired lock time.