What do mean by "turn on" the USB ports? They are already "on" (supplying power) and, if you have release 6.2 (which you should by now), they will initialize many USB network adapters and request configuration via DHCP. Following the link provided above will get the software to recognize the network.
If you want to use the USB ports for anything else (PPP connection, external hard drives, etc.), sorry, there is no supporting software in the system to do that.