Making a screen recoding on your iOS (iPhone and iPad) is really easy to do, but you need to check a few setting before you get started.

Turn on Screen Recording

1. Open your Settings app
2. Tap Control Center, then tap Customize Controls
3. Find Screen Recording in the list More Controls and tap the + icon next to it.

Note: By default the microphone is turned off. If you wish to record sound do the following.

Turn on Screen Recording Microphone

1. Open Control Center
2. Tap and hold your finger (3D Touch) on the Screen Recording button until a menu appears. 
3. Tap the Microphone button to enable it

How to Make a Screen Recording

1. Open Control Center by swiping down from the top-right corner of your screen
2. Tap the Screen Recording button to begin the 3-2-1 countdown and start your recording  
3. To stop the recording, tap the red Time in the corner and then choose Stop
4. Your video can be found in your Photos app