Audition only recording in the left channel

Setting the input source:

In this screengrab I've shown the location of the input source settings - and this goes for any track you want to record onto; you have to select an option. These are the mono source options on this laptop - yours will be different, but the principle is the same. If you had a stereo input option available, then you'd chose one of the [01S] options, and this would record onto both channels. But microphones are inherently mono devices, so you'd record it as a mono source. So how do you get it onto both tracks, you are asking?

The trick here is to start a new mono track in your stereo session (Multitrack>Tracks>Add Mono Audio Track) and select your mono mic as its input source. What happens now is that instead of having a balance control on the track settings, it will have a Pan control:

Adjusting this will let you position your mono source anywhere you want it in the stereo field.

The whole point of this is that it's flexible, and you can vary it according to your individual needs. The good news ia that once you've got a track layout that suits your working conditions, you can save it as a template and load it for the start of a new session, which will be exactly as you want it.