can I edit one channel in a stereo track? [SOLVED]

I want to mute out (or even delete) some background noise that has crept into just one channel on a stereo track. How can I do this?
Every time I try to select anything, it selects the section in both channels.


using Audacity 2.1.0 in Windows 10, installed from the .exe file downloaded.

To work on one track of a stereo pair you will need to split the track into separate Left and Right tracks. See:

Thanks Steve, brilliant.
As you might be able to surmise, I’m only an occasional user of Audacity, otherwise I would have known this already!!