Adding a background image on stage using only AS3

Hi guys, I need some help here. I'm quite a noob in AS3 and I am striving to make a game. A simple memory game, nothing complicated. And my problem at this point is adding the background image. I have everything else, all the code in one Actions frame on the timeline. What I need is a piece of code to take the image that I've created specially for the bg and place it behind everything that goes on over there. I looked through countless tutorials and pieces of code but I just don't get it, since nothing was saying how to do this one specific simple thing. Can anyone help me out? Thanks :)

Think what you are looking for is something like...

Code:

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addChildAt(bgImage, 0)

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