Windows will prevent users to install drivers without digital signature so to enable drivers without signature installation you need to disable driver signing enforcement.
1. Press Windows key + R, when the "run" box appear type:
shutdown.exe /r /o /f /t 00
2. Before it restart, a start up setting screen will appear. Make the following selection:
Troubleshoot — Advanced options — Start Up Settings — Restart
3. Select " Disable driver signature enforcement" after reboot.