Preloading in CS5 with an AS3 Document Class

[CartoonizeMyPet]

I've been working on a little flash app for the last couple of months and now the final hurdle is strapping a preloader on to the front of it.

The app is a fla/swf controlled by a Main.as document class written in AS3.

I originally wrote it in CS3 but after hitting my head against a wall for several days trying to figure out how to add a preloader I upgraded to CS5 in the hopes it would be easier. Several webpages (eg http://www.flashconf.com/category/flash-cs5/) mention being able to just specify a preloader.swf in the actionscript settings. I've tried adding mine but it doesn't appear to do anything when I simulate download or check it online. Should it really be that easy or am I misunderstanding. There's a surprising lack of info about for CS5.

The other option is to add one into the actual app swf, which I did find a guide for (http://active.tutsplus.com/tutorials...ngle-swf-file/) ...but its for CS3/4. I'm willing to give it a go as a last resort, but I wanted to check to see if there's an easier way for CS5.

Any help would be much appreciated, thanks!