Set up your phone to detect your face or another trusted device before you can unlock the screen.
Home screen, tap
, and then select and set up a screen lock.
This will be your backup screen lock method.
Security screen, tap
Confirm your screen lock.
Choose what you want your phone to detect before it unlocks.
Follow the onscreen instructions.
Lock phone after, and then specify the idle time before the screen is locked.
To help make Smart Lock more reliable and more secure, you can train
HTC One (M8)
to recognize your face in different situations, such as when you're wearing glasses or sporting a beard.
Smart Lock, confirm your screen lock, then tap
. Follow the onscreen instructions.