Go to Settings and tap FaceTime.
Turn on FaceTime and tap “Use your Apple ID for FaceTime.”
Enter your Apple ID and password.
Learn more about Apple ID
Tap Sign In.
Your phone number and all email addresses associated with your Apple ID will be displayed.
Note: Your phone number will be displayed only if you are setting up your iPhone, or if you are setting up another iOS device after you’ve set up your iPhone.
Choose which email addresses and phone numbers you want people to use to contact you for FaceTime calls.
Scroll down to Caller ID. Choose which email address or phone number you want to appear during outgoing FaceTime calls.