The primary way any user can secure his phone is by setting up a screen lock. The type of screen lock that can be implemented varies, it can be a pin number, a pattern or a password, these types of screen lock will restrict unauthorized users from your device. To set up a screen lock go to Settings. Go to Security and Location. Go to screen lock and set up the type that you want. Important: Please do not forget your pin/password/pattern or you might be permanently unlocked out of your phone.