Hook up your RRC control to your PC via the supplied USB cable. If you haven't done so before your PC will install a bunch of microbit drivers and after a time your device manager will have some new COM ports.
In my case I get
RRC 1258 COM0 (COM16)
RRC 1258 COM1 (COM13)
RRC 1258 COM2 (COM6) Let's use this one as COM2 is normally unused.
RRC 1258 COMExtra (COM14)
Yours may be different but the important thing to note is each RRC COM port is mapped to a PC COM port.
Make up a cable to connect your rig body to COM2. There's plenty of detail in the RRC guide and your radio guide about the connections.
Remote in to your RRC control and configure COM2 for the correct mode, baud, bits, parity. Also set "Use USB Com Port as COM2" to yes.
Remote in to your RRC radio and configure COM2 for the correct mode, baud, bits, parity.
It should be obvious that the settings for both RRC boxes should be the same and they should match the serial settings in your rig.
Now the magic.
Leave the USB cable from RRC Control plugged in to your PC.
COM6 (in my case) on the PC is mapped to COM2 in RRC and COM2 in RRC is connected to your rig.
If you have all the above set correctly you will be able to open COM6 on your PC with whatever control program you want and manage your rig.
Harder to write than it is to do.