In Flash player there's no pop-up window, if you need something like that you have to create a java script pop-up function in your web page and call it in ActionScript..
In your case I think you don't need to do that just use some function to show and hide the window inside the swf file..
For example:
var window_mc:MovieClip = new MovieClip();
var textField:TextField = new TextField();
var textFormat:TextFormat = new TextFormat();
textFormat.font = "Arial";
textFormat.size = 15;
textFormat.color = 0x666666;
textField.text = "Your text here..";
textField.wordWrap = true;
textField.setTextFormat(textFormat);
textField.width = textField.text.width +5;
textField.height = textField.text.height +5;
window_mc.addChild(textField);
window_mc.x = 200;
window_mc.y = 100;
window_mc.visible = false;
addChild(window_mc);
Now the pop-up window is on the stage, you can use window_mc.visible = true; to show it whenever you want, and window_mc.visible = false; to hide it.