To disable signing policy and install unsigned drivers on Windows 10 you have to change boot options. F8 menu in booting is not working any more.

You have to boot it to disable driver signature enforcement. This will disable enforcement for one time driver installation. There is a lot of options to reboot system in “Advanced startup” mode:

  1.  Go to Settings -> Update & Security -> Recovery -> Advanced startup -> Click Restart Now:
    settings menu advanced start-up
  2. Click Start menu -> Power Icon -> Hold SHIFT and click Restart
    shift+restart advanced start-up
  3. In command line put:
    shutdown /r /o 

  4. Boot from installation media (CD, DVD, USB Pendrive) and choose Repair your computer:
    advanced start-up from bootable usb pendrive
  5. Boot Troubleshoot from manufacturer recovery (sometime you have to choose Start-up repair to show Start-up  settings)
  6. Enable Legacy boot options menu and press F8 when system start-up
    1. Run cmd as administrator
    2. Put in command line to list all vailable systems:
      bcdedit
    3. copy identifier and replace {default} with current or your id like {123ffff….}
      bcdedit /set {default} bootmenupolicy legacy
    4. To recover normal booting put command:
      bcdedit /set {default} bootmenupolicy Standard

When you boot Advanced start-up click in order:

  1. Troubleshoot:
    troubleshoot1
  2. Advanced options
    troubleshoot2
  3. Start-up settings
    torubleshoot3
  4. Restart
    troubleshoot4
  5. Click 7 or F7 to Disable driver signature enforcement:
    torubleshoot5

Manually drivers installation

  1. Disable drivers signing policy if it necessary
  2. Go to Device manager:
    1. Start -> Run: devmgmt
    2. Right click on start -> Device manager`
    3. System -> Device manager
  3. Right click on device which you want to install driver and Update Driver Software:
    device-manager1
  4. Click Browse my computer for driver software
    device-manager2
  5. Let me pick from a list of device driver on my computer
    device-manager3
  6. Pick Show all devices
    device-manager4
  7. Click Have disk and browse for any .inf file in drivers directory, windows will find correct driver by pid and vid:
    device-manager6
  8. Choose correct device
    device-manager7
  9. In Windows security warning pop-up  window click Install this driver software anyway
    device-manager8
  10. Done:
    device-manager9

Permanently disable driver signature enforcement

Run cmd as administrator and put:
bcdedit /set testsigning on
Reboot

It will allow install any drivers and will enable watermark.