How to enable two-factor authentication for logging in to Apple ID

The system must be updated to iOS9.3 or above.

1. In Settings-iCloud-Password & Security, you can see the option to set up two-factor authentication.

2. Click Continue.

3. If a prompt appears because your current Apple ID has been logged into other non-iOS9 devices, click "Open Still".

4. If the current Apple ID has not been bound to a credit card, just click "Open Anyway".

5. Add your current mobile phone number.

6. Enter the SMS verification code received.

7. Two-factor authentication is successfully turned on, but it should be noted that you must add a few more numbers to the "Trusted Phone Numbers" so that you can quickly log in to your Apple ID even if your phone is lost. Change the password and use the backup mobile phone number to receive the verification code for operation.