Open Settings
Tap Control Center
Tap the plus icon next to Screen Recording if it is not already included
Swipe down from the top-right corner of the screen to open Control Center
Tap the Screen Recording button
Wait for the 3-second countdown
To record with sound, press and hold the Screen Recording button, then tap Microphone On
To stop recording, tap the red status bar or red clock at the top of the screen
Tap Stop when prompted
Find the recording in the Photos app