Use a Security Key With Your iPhone or iPad

How to Use a Security Key With Your iPhone or iPad (and Why) – By Jordan Gloor How-To Geek
To register a hardware security key with your Apple ID, open Settings and go to Password & Security > Add Security Keys. Follow the onscreen prompts, then you’ll need to have your security key with you every time you log into your Apple ID.
Did you know you can secure your Apple ID and other services on your iPhone or iPad with a physical security key? These keys bolster security and simplify two-factor login.