Not sure what your asking since you answered your own question.
Buy an Ethernet switch (the hub) and run an Ethernet cable to it from the Wireless G router. Connect one end of the Ethernet cable into the Wireless G router's LAN port and then connect the other end to the Ethernet switch's LAN/Uplink port. Then connect the PC(s) or other network devices to the Ethernet switch.
I have a 3Com hub that I tried this with and did not get an internet connection.
Check the ports on the back of the hub, usually one of the ports (usually the one at the right or left end) is designated the uplink port for connecting the hub to another hub, router or switch. If the hub is really old you may need to use a "crossover" Ethernet cable to connect the hub to another hub/router/switch. Or there may be a button to push in (or out) to set the port as the uplink port.