When purchasing your copy of Windows 8 or 8.1 online, you will receive an email (via the email address you provided at the time of purchase).
If buying a copy of Windows 8 or 8.1 on a CD or DVD, you should find the serial key on a card inside the box.
Getting a computer from an approved dealer, and you can’t see the sticker, ask the dealer to provide the Windows 8.1 product key.
In case of purchasing a computer with Windows 8.1 pre-installed, you should find your Windows 8.1 activation key somewhere on a sticker on the computer.
You can find your Windows 8.1 product key in the following places: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX How to Find Your Windows 8.1 Product Key