Just remember to enter those discount codes when checking out!
How to use your license key when it arrives:
After payment, the buyer receives an OEM product key to the email specified during registration, which can be activated directly in the Windows 10 system itself.
Head to Start > Settings > System > About the program > Change product key (in this menu you need to enter the received OEM key). The operating system itself, by the way, can be downloaded from the official Microsoft website.