Want to protect your phone against unauthorised use? Create a security code, and set your phone to lock itself automatically when you're not using it.
Select Settings and Phone > Phone management > Security settings > Phone and SIM card.
Select Phone autolock period > User defined, then set how long before the phone locks itself.
Create a security code using at least 4 characters. You can use numbers, symbols, and upper and lower case letters.
 | Tip: To type in letters or symbols, press and hold #. |
Keep the security code secret and in a safe place separate from your phone. If you forget the security code and your phone is locked, your phone will require service. Additional charges may apply, and all the personal data in your phone may be deleted. For more info, contact Nokia Care or your phone dealer.
On the home screen, press the power key 
, select Lock phone, then type in the security code.
Press the lock key, drag the lock screen left or right, type in the security code, then select OK.
If the lock key is out of reach, press the menu key instead.