I use Mimic and Carrara all the time, but I don't use the sound features in Carrara, so I can't answer your question directly.  Much like GKDantas, I use a video editing software package to marry the sound and picture.  Audition is a sound editing package; you'd need to be using Premiere Elements or Premiere Pro (or other editing software -- Vegas, iMovie, etc) to put the sound and video together, after you've rendered the file from Carrara.  You can use AfterEffects for this, as well, but again, it's not software that's designed for audio and video work.

The sound features in Carrara are a nice thought, but for proper alignment and such, a video editing package is the answer.