Question re: Random Movement in AS3 Tutorial

Getting back into Flash development after a prolonged absence, I was playing around with kirupa’s excellent “Random Movement in AS3” Tutorial.

So far, so good. This bit of code adds the instances of blueCircle on my stage

[COLOR=#000000]this[/COLOR].[COLOR=#000000]addChild[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]blueCircle[/COLOR][COLOR=#000000])[/COLOR];

What has me stumped now, because I can not remember for the life of me, is how I control on what layer within the stage my circles get created. How would I have to formulate the code above if I wanted to have all instances of blueCircle created on a layer called “circles”?

Thanks much!