One-sided stereo to mono track? [SOLVED]

I imported an aiff stereo file. Then I sang using a microphone through my Mac’s built-in input - which is stereo. The recording was fine but because mics are mono, it only recorded on the left channel of the stereo track. There is nothing in the right channel. I want to pan the vocal track so it plays back center, so I’m thinking I should try to convert it to a mono track. How can I do this? Maybe there is some way of selecting just the left channel of the vocal track and copying to mono? You can’t copy a stereo track to mono. Thanks.
*** I’m on High Sierra, using Audacity 3.13 on a Mac Pro mid-2010.***

“Split to mono” from the track’s dropdown menu (See:
Then delete the empty track (previously the right channel), by clicking on the [X] in the top left corner of the track.

Thank you, Steve!