Changing Your Screen Lock
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 can't remember your unlock sequence, after 5 attempts, tap the Forgot button (at the lower-right corner of the screen), then you can unlock the phone using your Google Account (if you activated it on the phone) or your Backup PIN that you created when you set up the screen lock sequence.
Enter your Google Account username and password, then tap Sign in.
Enter your Backup PIN, tap Done (at the lower-right corner of the keypad) or then tap OK (below your Backup PIN entry).