Concerning to WX-200 monitoring software,
Choose the software you consider the best.
Now we come to the RS232 cable connection to PC.
Check your CPU's backside for a 9-pin green-colored port.
This is the standard RS232 port which comes embedded with every PC.
If your PC doesn't have the port, check a suitable RS232 to USB connector for you.
Or if you are an "electric critic", just short the USB's 2nd, 3rd and 4th pins with the RS232's 2nd, 3rd and 5th pin. It would definitely work for you in no time.