Copy sound track to empty track in Premiere Elements 12

I have track from one video camera that only has sound in left track. Very noticeable against the other video clips. Cannot boost the gain enough to match other clips. I see plenty of discussions in Premiere Pro saying to just "fill left to right" in audio mixer. But that does not exist in Elements 12. I do not have audition, or other sound editing software. Can anyone help point me right?