how to fix bad sound in a video

[lupa]

I went to a concert recently and I got some great footage on my video camera, but the sound on the videos is completely messed up! it is very buzzy and it is hard to hear the music. (it was very loud at the concert! that is probably the reason why) anyhow is there any way that I can get rid of the noise in the videos?
i tried to download Audacity but I don't really know how to use it.
please help me, I refuse to give up the music is just too good!

every answer is appreciated