How to turn on the record screen function
Go to Settings > Control Center > Customize Controls, then tap green plus icon next to Screen Recording.
How to record your screen
You should know that some programs do not let you record.
Swipe up from the bottom edge of any screen. On iPhone X or later or iPad with iOS 12 or later, swipe down from the upper-right corner of the screen.
Press deeply on gray record icon and tap Microphone.
Tap Start Recording, then wait for the three-second countdown.
Open Control Center and tap red record icon. Or tap the red status bar at the top of your screen and tap Stop.
Your captured video will be saved in your Photos app .