It's very easy. The converter board needs 5V to power it. You can grab that from the PC's power supply, if that is what you are using. I still had my arcade switcher in there so that is where I grabbed my 5V from.
The CGA video out on the converter board is just 5 pins. You can get a harness made, but I just soldered wires to mine. From right to left is RED, GREEN, BLUE, GROUND, SYNC. Those wires go directly to the CGA monitor chassis video input. My Wells Gardner 25" needed the "SYNC" wire from the adapter to go to both negative H Sync and negative V Sync on the chassis.
Plug the converter to any VGA video card, does not matter how new. I would keep the resolution way down though because small text is hard to read on a CGA monitor. I think my Windows is set at 640 X 480.