You can set up a screen lock to secure your phone. Each time you power on your phone or turn on the screen, you'll be asked to unlock it.
Touch Screen lock and select the type of lock you want.
Some lock options aren't available if you added a VPN or a work (corporate) email account to your phone.
No lock:
Lock:
When you're using any of the 3 locks, you can also unlock with your fingerprint sensor and set your phone to automatically unlock in certain conditions.
If you're using a PIN, password or pattern, you can:
If you forgot your PIN, pattern or password, try these troubleshooting steps.