Your surround sound AV receiver has no TV tuner, so the coax signal won't do anything for it. You need an external tuner box that has audio outputs, and more specifically, if you're looking to get any kind of "real" surround sound (Dolby Digital or better) out of it, it will need to be able to decode the DD signals and output them either via optical or coaxial digital audio outputs.
On the left, next to the Ethernet port is a port labled Digital Audio Output. This accepts a "TOS-Link" fiber optic cable that carries multi-channel digital audio.
The orange RCA plug at the top is a Coaxial Audio Output. It carries exactly the same information as an optical output, but uses a standard RCA cable instead of a fiber optic cable to do so. There are devices that can convert from one format to the other.
If you only use the white and red analog RCA jacks, you'll only get stereo sound.
Oh, and an external tuner should be able to tune 2-13 VHF, 14-69 UHF, and 2-125 Cable, and these days, you should get one that is also capable of tuning digital (ATSC and if possible, QAM) signals.
Note that only a few non-cable-network shows use surround sound, but the premium movie networks (HBO, Showtime, Cinemax, Stars/Encore) transmit Dolby Digital for most movies.