Create an instance name in AS3

1

I have a movieclip called bg_mc. I don’t want bg_mc to show up until I click the btn. When I click the btn it will perform a wipe.

Currently I have bg_mc on stage because I need to access its instance name. I can’t remember how to create an instance name in AS3. Please HELP!

import fl.transitions.;
import fl.transitions.easing.;

click_btn.addEventListener(MouseEvent.CLICK, loadBg);

function loadBg(evt:MouseEvent):void {
TransitionManager.start(bg_mc, {type:Wipe, direction:Transition.IN, duration:1, easing:Strong.easeOut, startPoint:4});
}