How to select one channel for amplifying? [SOLVED]

How do I select just one channel so that I can amplify the volume level? When I use the select tool, both L/R channels are selected. I remember being able to do this in the past but now I am not able to highlight either left or right channels.

Left-hand drop-down menu > split stereo track.

Do your stuff.

Menu > make stereo track.


Perfect, thank you!!!