Face ID With a Mask Has a Device Requirement
Apple supports Face ID with a mask on iPhone 12 or later running iOS 15.4 or later. Having iOS 15.4 on an older Face ID iPhone does not, by itself, add Apple’s mask option. On a supported phone, the setting is managed through Settings → Face ID & Passcode.
This distinction matters if two iPhone users read the same Mega888 update note but see different options. The iOS heading identifies the Apple software version; the phone model determines whether the mask feature is available.
If You Cannot See the Option
First check the iPhone model and iOS version. Then confirm that Face ID is set up on the device and look at the access options shown in the Mega888 version you use. The published note does not identify every app screen where Face ID appears, so do not assume it will be offered for every account action.
If you have forgotten your account password, use the recovery route provided by the service where you registered. Enabling Face ID on the phone will not recover an unknown User ID or reset that password.