Are these the connections on the sound bar: Analog Audio Input1x Stereo RCA, Analog Audio Input1x 3.5mm stereo mini jack, Digital Audio Input1x RCA (Coaxial), Digital Audio Input1x Optical (Toslink), USB Input1x USB (for .WAV Audio Playback?
And your objective is to bring in audio from Apple TV, a Cable box (?), and another TV probably via a selector switch that allows you to select which input audio source is to output to the Vizio Sound bar.
What audio outputs are available on each of the three source devices. Not sure about "Cable box" so please add some explanation there.
You may be dealing with physical conversions as well as digital/analog audio conversions.
Check these two websites:
They provide a good indication of what may need to be done.
Draw up your own sketch of devices and ports then start looking into the necessary adapters and a 3 way selector switch.