How to use new i12 without a home button (fingerprint reader)

Instead of Touch ID, you set up Face ID, which is faster and more secure.

Instead of the home button, there is a white bar in the center of the bottom of the screen. Swipe the bar up to get to your home pages.

Tap this link and read the iPhone User Guide for your model iPhone --> iPhone User Guide - Apple Support

With Apple Watch Apple added a link between the two devices to unlock your phone with a mask on. Otherwise, you'll have to enter your passcode. Apple will not make Face ID less secure. So if a good portion of your face is covered by a mask it can't authenticate your face to unlock the phone.

Do let Apple know your thoughts on this if you'd like --> Feedback - iPhone - Apple

You will be offered to use a passcode number if Face ID fails.

All well and good unless you are wearing a mask due to covid!!!