Man of prey translation under way - need help

[R@S]

In the small window where you select which layer you want to edit there's a tab called channels, at the bottom of that you can find the alpha channel. A little trick when working with this is to use the magic wand on the other channels to get the selection you want and the switch to the alpha channel and make the slection transparent(white) or not(red).

I hope that makes sense