Start the install process
Reboot for media
If you’re running Windows 7, or have Fast Boot disabled, insert your boot media and start your PC. Look for a ‘Press any key to boot from CD or DVD’ option (even if you’ve booted from a USB flash drive) – press the key and you should find the Windows install process starts.
Tweak boot options
If you boot back into Windows, restart your PC again, but this time press a key, such as [F11], when prompted to open a boot menu. Do so, select your boot media (choose UEFI if the option appears) to boot; otherwise, enter Setup to change the boot device order.
If Fast Boot is enabled, open Settings in Windows and navigate to ‘Update & recovery’ > Recovery, then click ‘Restart now’ under ‘Advanced start-up’. When the boot options appear, choose ‘Use a device’ to select your USB flash drive or DVD from the list.