Editing individual tracks

I have a stereo recording in which I’d like to vary the levels of one track only. Is there a way to do this? I only seem to be able to select both tracks. It’s probably in the manual, though I haven’t come across it.

Audacity 2.0.2
Mac OS 10.13.6

Split the track, apply the effects that you require to the two new single channel tracks, then join the tracks back together into a stereo track. See: https://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html

Thank you! Exactly what I wanted.