how do I do it? That is all.
Drag from windows or desktop to vse timeline or shift a to add, select add audio strip.
Make sure you view the console after importing an MP3. I have seen Blender spit out complaints about data with some of the MP3 files I use. If you see such complaints and are worried about synch (like with a voice over) try converting the MP3 to a WAV file. They seem to be complain free.
Okay and how can I export it with the video? What format should I use? Mpeg? I’d prefer avi if it’s possible.