First, it seems that you have not finished the Setup Assistant for Internet Viewing. This should be the first step to follow. This link will provide you with all the information you must know.
Since the Slingbox SOLO does not have a coaxial input, you do not need to scan channels. The following third-party link will provide you with the step-by-step instructions in order to set up the Slingbox for Internet Viewing with an Airport Extreme.
Port Forwarding SlingBox on the Apple AirPortExtreme