The only input the RCA has is the analog aux input.
If your TV has a headphone jack or analog audio out use it.
Most likely the TV has digital audio out (usually optical). You will need a digital to analog converter. Check the TV manual on how to turn on and configure the output. You may have to turn the TV speakers off and change the audio type to PCM stereo. Select a surround mode on the RCA that works with a stereo input. You won't get digital surround sound.