Step 1: Set up VPN
Follow directions of VPN software to create a LAN connection. Windows PC acting as RCForb Server should run the VPN server (or a thrid Windows PC on the same network.) Server and Radio PC's should be able to "ping" each other with VPN active
Test functionality of VPN by moving radio PC to hotspot/public wifi not on your home network. Connect to the VPN again and you should still be able to ping the Server PC