In order to fade away the layer, you'd do something like:
System > On layout start > Black Screen > Set Opacity to 100
System > Wait .5sec
Black Screen > Opacity 80
System > Wait .5sec
Black Screen > Opacity 60
etc.
So basically, every half second, you'd be lowering the opacity of the object until it reaches zero. At that rate, the screen will transition from black to invisible in about 3 seconds.
If the transition is too blocky or takes too much time, try something like lowering the opacity by 5 every .1 seconds. This would change you from black to clear in about two seconds, with a fairly smooth transition.
Or you could play around with fade. I haven't found a fade button yet, so...