This took me a while to get my head around this, from the written instructions. So I've make this (not so great but really quick) Tutorial on: Real Time Audio Adjustment while still recording with a Canon 5D Mkii. I hope it helps, this is a great and much need feature that Im really thankful to the Magic Lantern team for adding.
Don't use https with vimeo :D
Nice one thanks!
Nice! Stickied this topic as many users seem to have trouble understanding how it works.