Swipe down from the top of the screen twice to open Quick Settings
Look for the Screen recorder icon
If you do not see it, tap the Edit button or the plus icon to add it
Tap Screen recorder
Choose your sound settings if prompted
Tap Start recording
After the countdown, begin using your phone
To stop recording, tap the floating stop button or open the notification panel and tap Stop
Find the recording in the Gallery app or Photos app under Screen recordings