Placing MC's on scene w. AC3

Hi!
I’m wondering if someone could help me. I just started working with AC3 and I find it quite hard. I know some AS2 but it was kind of a long time since i’ve worked with it…

What I need to do is to with actionscript randomly place a bunch of invisible MCs on the scene - I guess by using a for-loop (?). When clicking on the scene (anywhere), the MC on that spot shows and starts playing. When it’s done playing it should go back to invisibility.

So, how do i do this?

Thanks
a.