Glance screen is a feature first requires an updated version of Display system app to add enhancements to the Amber update. You will get the app update notification on Store tile shortly after update. Once Display sys app updating is complete, Glance appears in the settings menu (If not, you need to restart the phone).
Change the setting for Nokia Glance Screen, go to Settings > glance. You can choose Peek for display when you hand is held over the phone (this option used the proximity sensor), Interval (timed) for a fifteen minute display of the Glance screen after the phone locks or Always on.
Due to hardware restrictions Nokia Glance will not be available for Nokia Lumia 520, 521 and 625.