How do I activate Windows? / Where is my Windows Product Key?
You shouldn't need to activate Windows on a new MAINGEAR system -- it's already activated out of the box. If you're seeing a Windows activation notice on your screen, your system should automatically activate within a few hours once connected to the internet.
If you need your Windows Product Key, it can typically be found on a sticker on the back of your system (or the underside, on laptops).
If you make major hardware changes to your system, please see this article on Microsoft.com regarding reactivating your Windows Product Key if necessary: https://support.microsoft.com/en-us/help/20530/windows-10-reactivating-after-hardware-change