The Modem should connect into the routers WAN port using a RJ45 network cable
Your Local PC can connect to any other port on the router using a RJ45 network cable
Your remote PC can connect to any other port on the router using your long RJ45 network cable
Turn everything off, then power up in the following order with 30 seconds between:
Modem
Router
Local PC
Remote PC
If you have any problems let us know