AS3 - displaying movieclips from library

I have several movieclips in my library that I want to load, one after the other in kind of a scrolling animation on to the page, but I can not seem to be able to write the code to make this happen.
I know it has something to do with an Array and addChild(), but no matter what I do I always get some sort of DisplayObject error.

I have been searching for a few days on how to do this, but with no luck.
Could someone point me in the right direction please?