Ultimate Transparent

I did buy Ultimate UnWrap which seems to be a good tool and easy to use.
Anyway I could not figure out how to get some parts of the texture(s) transparent. I'm using Paint Shop pro to make a partially transparent texture(s) as png files, but when loading the mesh into blitz (also while loading the texture into UUW), transparent areas look black instead of transparent.
I think it should be easy, just can't figure out what's the problem in my brain :=)

i usually just export the chanel as bmp(bw/greys, in Adobe or Gimp), force the material to have opacity slot.

In 3d preview window activate smooth textured.

menu at the right :

material...maps...diffuse...one difusse bitmap, and one opacity.