Denon AVR-1800. A friend

Denon AVR-1800. A friend set up the receiver, playing a DVD, TV, and CD, and cassette player. There are two Infinity tower speakers and a center speaker, with subwoofer. Everything went well, with all speakers working using the (5.1 surround) setting. I added two satellite speakers, one worked, but had trouble getting both to play at same time on any setting, and then one tower speaker wouldn't play. After pressing buttons on the receiver and the remote, I am now not getting any playback through the receiver for my TV. (6CH IN TV) is the setting. What do I need to do to get the TV playing through the receiver?