Exactly as Ryclark says, with the addition that, if my memory of the Fast Track Pro is accurate, from the control panel you can select whether to put the stereo outputs at the top or bottom of the list to speed the selection for future sessions.

Due to the messy handling of Audio in Windows, you may need all three.

You don't say what version of Windows you have but if it's Vista or Windows 7 you may need to go to the Audio Control section of the Windows control panel to make sure it's displaying the M Audio on both the Playback and Recording screens.  If they're not, click on the white area and tick Display Disable Device and Display Disconnected Devices.  Select the M Audio as the device to use.  (You may find all this is okay but worth a check).

In Audition, go to the Edit/Preferences/Audio Hardware menu and select ASIO as the Device Class and the M Audio as the Device to use.

Finally, the M Audio Control panel will let you select which channels to use and also the channels to use as default (i.e. at the top of the screen).

As for the insert  section, those are to add outboard processors (like compressors) to the first two inputs on the M Audio (and they take special TRS jacks...one TRS to two TS jacks).  The RCA/Phono and the TRS output jacks can either be used to feed your monitor speakers.  FYI, there are also RCA jacks for digital but you can ignore these unless you need them.

Your set-up for the Fast Track is correct.

You are only recording a single channel and you are presumably plugging in the mic into input 1 on the Fast Track.  You are then arming Audition to record a STEREO track, not a MONO track, thus you are only hearing the left channel because you only recorded the left channel.   When recording a single microphone on the Fast Track, have Audition record only a MONO track.  To record a MONO waveform, open Audition and in the upper lefthand corner click on Waveform.  A window will open called New Audio File.  You will see different parameters to be selected.  Audition defaults to STEREO channels.  Change this to MONO and hit OK.  You have now armed Audition to record a MONO file. 

If you have already recorded a take that you like, but wish it to be MONO rather than STEREO, then you can open that track in Edit View.  You should see that your waveform has two tracks, with your recording on the Left (top) section and nothing on the Right (bottom) section.  Go up to the Menu Bar at the top of the window, select Edit, then in the Edit Menu select Convert Sample.  In the Convert Sample Type window, you will see a Presets dropdown menu at the top.  Open that and select Convert to Mono (Average).  Now, before you click on OK you must go to the Channels section in the middle of the window and click on the little white triangle next to Advanced.  You will see percentages for Left and Right.  Make the Left 100% and the Right 0%.  Then click OK at the bottom of the window and your waveform will now be a MONO waveform.