So you're using FaceTime for the first time on your iPad. Well, after you tap the app’s icon from the Home screen, you’re required to sign in to FaceTime using your Apple ID, which can be your iTunes Store account, iCloud ID, MobileMe account, or another Apple account.
If you don’t have an account, tap Create New Account to set one up within FaceTime. You also must supply an e-mail address that callers use to call you from their own FaceTime-capable iPads, Macs, iPhones, or iPod touches.
If this is the first time you’ve used a particular e-mail address for FaceTime, Apple sends an e-mail to that address to verify the account. Click (or tap) Verify Now and enter your Apple ID and password to complete the FaceTime setup. If the e-mail address resides in Mail on the iPad, you’re already good to go.
If you have multiple e-mail addresses, callers can use any of them for FaceTime. To add an e-mail address after the initial setup, tap Settings→FaceTime→Add Another Email. In fact it’s often a good idea to allocate separate e-mail addresses for FaceTime, assuming you have more than one Apple product that can take advantage. That way a call to you when you’re on your Mac, for example, won’t ring on the iPad instead.
You can turn FaceTime on or off within Settings, but if you don’t turn it off, you don’t have to sign back in when you launch the app.