Hi Wolfie Wolf
What I think that you had just replaced the defective hdd with a new hdd with no OS installed.
Get a usb thumbdrive, 8GB or greater and use another PC to make a win10 usb installer.
Follow the below steps to make win10 installler.
[guide|89181]
Maintain in UEFI settings on your bios, and secure boot on.
once the usb has been created, allow it to boot from usb and follow the instructions to perform os installation.
run windows update to complete some drivers updates / gaps.
if you are unsure, update us here. we will be glad to help you.