My situation is this:

1) Captured VHS tape using virtualdub into AVI file format

2) Using Tmpgenc with settings: ES (video+audio); dvd ntsc (mpeg-2 720x480 29.97fps 2pass VBR) created 2 files: M2V video file and wav audio file
3) Authoured using neoDVD
4) Burned using Nero

Problem:
Both the authored files and the burned DVD have the video but no audio.

Looks like I need to import the audio manually into neoDVD, but how?