In most cases, you'll enable FaceTime as part of the overall setup process you go through the first time you turn on a new iPhone, iPod touch, iPad, or Mac. If you don't, and you later change your mind about it -- or if you do, and you change your mind! -- you can also enable or disable FaceTime at any time. If you're worried about children having access to FaceTime, you can even lock it out completely using parental restrictions.
