Say, for example, I make a really cool animation. I know how to do the video using blender (not really, but i can figure it out … %| ) So now i have this avi file. how do i add sounds, music, and all that good audio stuff?
P.S. The question is not where i can get the audio files, it is how to add and mix them into an avi file. ( I had to include this P.S. because i asked my friend this question and he gave me a sizeable list of sounds :x )
get a video editor. there are some freeware ones listed here
https://blenderartists.org/forum/viewtopic.php?t=1522
if you don’t mind spending some money then Adobe Premier is good. personally i use ddclip which is free.
d52477001
maybe a better place would be Q & A forum 
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Avid is releasing a free version of its high end video editing software; however, it is limited to two tracks. It’s still an excellent piece of free professional software.
I use some MPEG editor. It can only take in a video track and an audio track, but I use it if I publish animation. (So far, there’s been a grand total of 1.)