[Gimp-user] using Alpha Layers to change white to transparent

[Brenton]

This picture shows what I have now:

http://brentonboy.com/misc-pics/layers.png

I made the mistake of creating the image to fade to white. Now I want to use
alpha transparency to have it fade to transparent, for use on non-white
backgrounds. I know there must be a way to change those faded white layers
into fading transparencies.

I have played with the alpha layer thing a lot, but I don't know what
settings to use, and it seems not to do anything anyway. 

Thanks in advance.

-- 
Brenton