Step 3: Get Your Login Info
If you're moving from iOS 8 or older to iOS 9, you're going to need to login to your Apple account during the setup. If you're coming from iOS 8.4.1 or older, iOS 9.0.1 or iOS 9.0.2, you'll need to have the devices passcode to start the download. Have all of that information on hand before you make your move.
If you're coming from iOS 8.4.1 or older, you'll also have to have your login information for your various applications handy. Even if you restore from a backup, your applications will log you out so make sure you know your passwords before installing iOS 9.0.2.