Windows wont "fit" on a cd. Did you mean DVD?
How did you make the DVD? Did you use Microsofts Media Creation tool? It and the Win10 download are free. You won't even need to activate Win10 if you don't have a key.
https://www.microsoft.com/en-us/software-download/windows10
If you have a flash drive 4+gb in size, use that. Its way faster then using a DVD.
Ok so once you get a valid install DVD/Flashdrive, Turn the PC off and disconnect all hdd or ssd's except the one you intend to be your main drive (C
Enter the bios and set the primary boot disk to be that C: drive. Do not set the DVD/Flashdrive with the installer on it as the boot drive.
When you start up the PC with this DVD/Flashdrive installed, watch the bottom of your screen. At the same time that it says 'Press xx to enter Setup/Bios' there will bew another option to select a drive to boot from. It's technically called Boot Override but the message at the bottom of the screen is short and might say something different like select boot. Whatever it says, press that F-key. It's F11 on my motherboard. Asus I think is F12
The Windows installer will start up and you follow the prompts from there.