It's a bit of a design issue but you actually need to go into Settings -> Notifications -> Do Not Disturb to actually setup your DnD preferences including autom

It's a bit of a design issue but you actually need to go into Settings -> Notifications -> Do Not Disturb to actually setup your DnD preferences including automatic scheduling. Then, you can flip it on or off from the main Settings screen. It does stop your app notifications from disturbing you but your phone has to be locked for that.