If both TV and Onkyo are ARC capable (consult the manuals) then hook up both HDMI ARC designated ports, go into both menus and be sure to enable ARC, and you are good to go.
If both TV and Onkyo are ARC capable (consult the manuals) then hook up both HDMI ARC designated ports, go into both menus and be sure to enable ARC, and you are good to go.