Here is the guide to activate Windows 8 or 8.1 with a product key, follow these steps:
1) Click the Start button on your screen and type “PC settings” in the search bar.
2) Select “PC settings” from the results.
3) Click on “Activate Windows.”
4) You may be asked for an admin password or to confirm your choice.
5) Enter your Windows 8/8.1 product key and press “Next.”
6) Select your location from the drop-down list, and then select “Next”.
7) Then you will see Installation ID which is 63-digit numbers, now you can submit your Installation ID on Getcid.info.
8) After receiving your Confirmation ID, you can enter your Confirmation ID, and your product will be activated.