Frustrated!

A gal stops making icons for a month and she forgets the easiest stuff via cs2??!!

oKAY, I'm desperate now. How do you get this done:                




I have all the brushes- for stuff like this and yet when I click it over an image, it instead is INVERTED. The other way around and its frustrating me because Ive done this before! Its easy!...But I've forgotten how to do  it.  

Help!