You may not have the screen recording function even though u updated your iOS. The video will teach you how to get the function. First you go to settings. Then control panel. Under control panel look for screen recording. Add that function to control panel. After that when you flick up you should be able to see the screen recording function.
Slide your finger from the bottom of the screen up
Press on the circle icon. It will start recording.
When recording you can see the red bar above
Click on the red bar to stop recording.