Making a Gmod Machinima:Audio help!

I know how to make a Garry’s Mod Machinima.Like recording,setting everything up,etc.Except one problem.I can’t figure out…where to get sound effects,and how do I put audio/sound effects in the video with music playing in the background.How the hell do I do it?Do I need to use something else then Windows MovieMaker?Please help for christ’s sake.

NOTE:Can someone give me a source for sound effects like,“HAAAX” or"IMA FIRIN MAH LAZAR" and all the other retarded memes?

Read the credits of “Gmod idiot box” any video. And it shows what tools DasBoSchitt used to create sound and everything.

Try getting a demo of something. Premiere pro or sony vegas. I dunno…

Anyways here is premiere pro. Just click the yellow and black “try” button I believe.
Though I really don’t know what one you SHOULD use. look into that yourself or something then… :3

I have Vegas Pro 9.I just need sound effects…like punching effects and yaddah yaddah…

There’s website that can be found on Google filled with heaps of sound effects.