Using two-factor authentication helps prevent others from accessing your next to the phone number.
When you’re finished making changes, tap Done.
Trusted phone numbers don’t automatically receive verification codes. If you can’t access any trusted devices when setting up a new device for two-factor authentication, tap “Didn’t get a verification code?” on the new device, then choose one of your trusted phone numbers to receive the verification code.
Go to Settings Two-factor authentication for your Apple Account