If you don't have Windows 8.1 Professional edition already installed, we recommend you first download and install it from here: https://www.microsoft.com/en-us/software-download/windows8ISO
To Activate Windows 8.1 Professional with OEM Key follow this:
1.Click on Start Button and type "PC Settings"
2.Select "PC Settings" from results
3.Choose Activate Windows
4.Enter the Product Key you received after purchase
5.Done, now your Windows is activated
If you encounter any error after entering the Product Key then follow this:
1.In Search type "slui 04" and click on it
2.Select your region from the dropdown
3.Call the toll-free number and they will guide you and provide you with your Confirmation ID
If you encounter any other errors or face any issues, please make sure to contact us through our Contact page or email us at "support@premiumcdkeys.com". Our support team is available 24/7 at your service.