Go to Settings and tap FaceTime.
Turn on FaceTime and tap “Use your Apple ID for FaceTime.”
Enter your Apple ID and password.
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.
FaceTime works right out of the box — no need to set up a special account or screen name. And using it is as easy as it gets. Let’s say you want to start a video call with your mom. Find her entry in your contacts and tap the FaceTime button. Or simply tell Siri, “FaceTime with Mom.” Or maybe you’re already talking to her, and you want to switch to video. Just tap the FaceTime button on the screen. Either way, an invitation pops up on her screen asking if she wants to join you. When she accepts, the video call begins. It’s all perfectly seamless. And it works in both portrait and landscape views.
Two cameras made for video calling.
iPhone, iPad, and iPod touch each have two built-in cameras, one on the front above the display and one on the back. The front camera has been tuned for FaceTime. It has just the right field of view and focal length to focus on your face at arm’s length. So it always presents you in the best possible light.