Create a bootable USB stick with Windows 10 on it .
If the computer won’t boot , power it off .Turn it on & press whatever button to get into the BIOS settings .Like F5 , F11,F12 etc .Change the boot sequence to put the USB as the first thing to boot .Turn off the computer , stick the USB key in &, power it up it should go straight to installing Windows 10.
Thats just one thing you can do . Could you take a picture of the screen you get when you power it up ?
Also you could go into Safe Mode & select the Repair option there .