I can't for the life of me figure out how to disable Embark NYC's push notification. My biggest problem now, however, is getting push notifications from Letter

I can't for the life of me figure out how to disable Embark NYC's push notification. My biggest problem now, however, is getting push notifications from Letterpress at 4AM, because the person I play with is on the other side of the continent. There should be an adittional setting to require permission for a specified window of time like, say, 1AM to 8AM.