step 4: u should have 3 layers now. 2 with the picture and another with the black box.
Go to the layer with the black box and select the black box.
Now switch to one of the layer(should be the second one) with your picture. Press Ctrl + I
Press Delete
Done
As for feather : http://paintdotnet.forumer.com/viewtopic.php?f=16&t=22819&st=0&sk=t&sd=a&hilit=feather