Two-Factor Authentication strengthens the security of your Apple ID by preventing anyone from accessing or using it, even if they know your password. With Two-Factor Authentication, one of your trusted devices generates a one-time code when you make a purchase or sign in to your Apple ID, iCloud, iCloud.com, iMessage, FaceTime or Game Center account on a new device. Two-Factor Authentication is also required for Auto Unlock so you can unlock your Mac by wearing an Apple Watch.
In this tutorial we'll show you how to protect your Apple ID with Two-Factor Authentication or, if you're still using the older and less secure Two-Step Verification, upgrade to Two-Factor Authentication.