Uh, I have no idea what Kinji is talking about. What you need to do is use alpha transparency. This is not available in Standard, but you said you have Extra so you're good to go.

Alpha transparency involves creating an alpha channel in the image to define transparency and then saving as a 32bit TGA image. Exactly how this is done depends on your image software. The common bit however is that black pixels in the alpha channel make those pixels in the image fully transparent, white is fully opaque, and the various shades of grey are accordingly semi-transparent. Thus, you can get a gradation of transparency (as opposed to just on/off) allowing for an anti-aliasing effect of the edges.