Regarding: Tween/AS Preloader

hi there!! i’ve got some trouble understanding the steps of the example.

the url is… http://www.kirupa.com/developer/actionscript/tween_as_preloader.htm

in step vii. Click on the box again, and apply this code in the Actions Panel:

onClipEvent (enterFrame) { gotoAndStop(int(_parent.getBytesLoaded()*100/_parent.getBytesTotal()));
}

i clicked on the box… but it says that “current selection cannot have actions applied to it.”

can anyone help me? thanks thanks!