Help connecting a Moterola Surfboard cable motem to a TP-link wireless router.

Hi. I have what maybe a silly question in the end.

I had Rogers install their internet today, and with it came a Moterola Surfboard Cable modem, It's working great, it has a cable line in, and the USB or Ethernet line out.

I though "Hey, it would sure be handy to have wireless" so I went and bought a TP-Link 108 M Wireless ADSL2+ wireless router.

The router has five ports on the back, four ethernet ports labled 1 to 4, and one "line" port.

So I assumed I'd have to plug the cable from the modem into the "line" port on the router, and voila, wireless internet.

However, the line in port on the router is for a phone cable, not an ethernet cable. Is there any way I can plug the line in cable into one of the 1-4 ethernet ports and have it work? Did I just buy the wrong router?

Thanks for any help you can give.

Rob.