1. To set a screen lock, from the homescreen, tap Security.
   
2. Tap Screen Lock.
   
3. Tap the Screen Lock toggle. 
   
4. Enter a four digit passcode, then tap OK.
   
5. Confirm the new passcode, then tap OK. 
   
6. To unlock the device, press the Power button, then tap the lock icon.
   
7. Enter your four digit Passcode.
   
8. If you forget your passcode, enter the an incorrect passcode 10 times to perform a factory reset. Proceeding will erase all of your cutomizations and settings. Tap OK.