Making 2D images have transparent sections?

[Lord Darkblade]

I am trying to make a new hud, or edit one that was half done from before, and I'm stuck. I have edited from this texture:

But when I get in game the parts of the image that are supposed to be transparent, aren't! Does anyone know the transparent image coridinates, e.g. 255, 255, 0 = yellow

The little I or H, depending on how you look at it, marks where the black should NOT be. The spikes are supposed to have no black surrounding them.

 

Any help would be great. Thanks