Setting up a lock on your device will help keep your information secure. A screen lock will prevent others from getting into your device unless they have the necessary credentials. If your device is requesting a PUK code, you need to contact your carrier to unlock your device. Removing your security lock will allow anyone to be able to unlock your device.
From the Home screen, tap the Apps icon.
Scroll to Settings.
Scroll to Security.
Tap Screen lock.
After this step, select your preferred screen lock.