To enable the Unlock with Apple Watch feature, open the Settings app on your iPhone, then look for the “Face ID & Passcode” setting. Once you flip this toggle, your Apple Watch will be able to authenticate your iPhone as long as the following conditions are met:
- Face ID detects a mask - Your Apple Watch is nearby - Your Apple Watch is on your wrist - Your Apple Watch is unlocked - Your Apple Watch has a passcode enabled
https://9to5mac.com/2021/02/04/iphone-face-id-unlock-apple-w...