Please check, which Windows Version you bought. You can find a hint on you invoice behind "Lizenz".
In Windows 8 and 10, Microsoft introduced a new activation method in which the license key is integrated in the firmware (BIOS) of your device. Our OEM Windows versions have this method.
When you run the Windows 8 or Windows 10 setup on a computer, the key is automatically retrieved from the firmware and therefore does not have to be entered manuall.
After you first connected to the Internet with the installed Windows, the product key is fully activated.
You can find your Windows license key on the outside of the computer case or the bottom of your notebook.
A part of the key is covered with a silver layer with the text "Microsoft".
This small silver box can be used to gently scrub, similar to a scratch card. Please do not exert too much pressure.
You can enter the now readable key as a new key during Windows activation.
The activation can be found under "System Control" - "System" or with the key combination "Windows key" + "Pause key". Please click on the button "Activate with new key" and enter the key of the sticker.