This article explains how to add screen recording option to iPhone 12 Control Center, and how to start and stop screen recording.
How to Screen Record on iPhone 12 / iPhone 12 Pro / iPhone 12 Mini and iPhone 12 Pro Max!
Before you record your screen on iPhone 12, you’ll want to add the option to your Control Center for easy access to the controls. Here’s how to do that.
On your iPhone 12, tap Settings.
Scroll down to Screen Recording.