How Do I Turn On Night Shift On My iPhone?
There are multiple ways to enable Night Shift as of its introduction in iOS 9.3. First, you can toggle by telling Siri to "Enable Night Shift". You can also turn it on via the Control Center. Just swipe up from the bottom of your screen to access Control Center, then tap the icon in the bottom middle of the screen (the icon looks like the sun with a crescent moon inside of it).
If you would rather schedule Night Shift instead of manually turning it on and off, launch the Settings app on your iOS device and navigate to Display & Brightness > Night Shift. Turn on Scheduled and select the timeframe for Night Shift to be enabled each day. You can also manually adjust the color temperature to fit your preferences.