Loading external swf into movie clip on button press

Im just making the switch to AS3 and i’m having some major problems loading in external swfs. In AS2 it was easy but from what i’ve found i’m just not understanding how it works in AS3. I have a movie clip that has my navigation in it that would call the external swfs for each section of the site, it also contains the backgound design for the site. I have my main movie set up for full browser for positioning. and i want to be able to position where my external swfs are loaded as well.

Any help would be much appreciated, i’ve been looking and trying to figure this out for a few days now.

thanks
Jake