Two-Factor Authentication is an extra layer of security for your Apple ID designed to make sure only you can access your account, even if someone else has found out your password.
Two-Factor Authentication ensures you can only login to your account on devices you trust – i.e. your iPhone, iPad, or Mac.
To turn it on, simply go to:
Settings > (tap your name) > Password & Security > Turn on Two-Factor Authentication
Now when your log into a new Apple device that you haven’t done previously – after entering your Apple ID password; you will be prompted to enter a 6 digit passcode that apple will send to one of the other devices you have previously used.
The six-digit verification code is automatically displayed on your trusted devices. By entering the code, you’re verifying that you trust the new device.
Once signed in, you won’t be asked for a verification code on that device again unless you sign out completely, erase the device or change your password.
Stay Safe, Have Fun, Enjoy.