From the Home screen, touch and hold the Recent Apps Key (in the Touch Keys bar) > Lock screen settings.
Tap Select screen lock.
Confirm your unlock information (if necessary).
Tap the desired screen lock option.
You’re prompted to enter your screen lock.
If necessary, enter a Backup PIN and tap Continue. Then confirm your Backup PIN and tap OK.
If you've set up a Microsoft Exchange account, you might only be able to use a password.
After 5 unsuccessful attempts to unlock your phone, you're prompted to enter a text phrase to confirm that you're trying to unlock your phone.
You have 10 opportunities to enter your unlock sequence. After 10 unsuccessful attempts, your phone will automatically perform a factory data reset and all of your personal files will be erased. You will be warned after the 9th unsuccessful attempt.
If you've set a Knock Code, after 6 unsuccessful attempts, you're prompted to enter your Backup PIN to unlock your phone.