Swipe down from the top of the screen to open Quick Settings
Look for Screen Record, Screen Recorder, or Record Screen
If you do not see it, tap Edit or the pencil icon to add it
Tap Screen Record
Choose your audio settings if prompted
Tap Start or Start recording
Wait for the countdown to finish
Use your phone normally while recording
Swipe down and tap Stop, or tap the floating stop button when done
Find the recording in your Gallery, Photos, or Files app