That appears to be the correct driver. Are you connecting the keyboard and turning it on before you try to install the driver?
Also, are you trying to connect to a USB hub? You can't use a hub, you must connect to the computer directly.
Additionally, if you're trying to use a Windows 8 tablet or laptop and it has one of those smaller USB ports, you will need to use a different type of USB cable, one that fits the USB port (USB-C?).
Note that if you're getting an unknown device error before installing the driver, I think you should still be able to install the driver. But since it's Windows 8, you might need to follow an install procedure specific to Windows 8. The zipped folder contains an Installation Guide document, but there don't seem to be any instructions which are for different versions of Windows (7, 8, 8.1, or 10), so presumably the given instructions apply to all 4.
One thing I see in the Release Notes for the driver is that the CPU should be 1.4 GHz or faster, and should also be an "Intel Core/Pentium/Celeron processor." Do you know what the CPU on your computer is?
Note that since you've got a Windows 8 computer, it might be possible to use an older version of the driver, as long as it's compatible with 64-bit Windows 8. I don't know if using an older version would help, but it might help if the older version has different hardware requirements that match your computer and CPU.