I think what he is saying is take the line out (ie audio video cables from the VHS machine into one of the line ins into the TV. This leaves the CATV or antenna F connector on the HDTV free. You simply hook up the antenna to this input and use it to get over the air HD signals.

When you want to watch analog cable, you must use the VCR as your tuner because your regular cable is plugged into the VCR. In other words, you must turn on the VCR and use it tune all of your analog cable signals. You need to change your TV from antenna input to the input that you plugged in the audio video from the VCR. I wish I could draw this out ... hopefully this makes sense.