Send to back

setChildIndex(example,0);

Bring to front

setChildIndex(example,numChildren - 1);

Relative to something else

var otherindex = getChildIndex(theotherthing);

//Behind that thing: 

setChildIndex(example, otherindex) //pushes the other thing forward
 //In front of that thing: 

setChildIndex(example, otherindex + 1);