To instantly enjoy all the pleasures of iOS 9, you need to register your gadget's UDID as a developer's one. UDID - is a unique identifier for Apple devices of 40 characters. It is unique for each iPhone (iPad, iPod Touch).
You can see it by connecting to iTunes, select your device in the left column. Look for the "Browse" serial number and click on it. You'll see a set of 40 numbers and letters - this is your UDID (press Ctrl + C or Cmd + C to copy).
Fill in this number in the "Serial Number" and click "Place order"