To begin, you must download and install the iOS 14.5 update on your iPhone.
open SettingsGeneral Software update
This applies to iPhone X and later, as well as Apple Watch Series 3 and later. You are not required to do anything with your Apple Watch. You’ll only need to make a few changes to your iPhone by following these steps:
On your iPhone, go to the Settings menu.
Scroll down and click on ‘Face ID & Passcode.’
Then look for and enable ‘Unlock with Apple Watch.’
When you enable this feature, your iPhone’s Face ID will unlock when it detects any face with a mask. This feature will only work if your Apple Watch is unlocked and nearby. When your iPhone detects a mask-covered face, it will send a haptic and notification to your Apple Watch to unlock it.