Newbie stuck

[rich2005]

Which bit of your earlier post did you not understand

http://www.gimp-forum.net/Thread-Just-le...928#pid928

Make sure your image has an alpha channel (transparency)

Layer menu -> Transparency -> Add Alpha Channel

edit: As an experiment

Open your image, just a single layer.
Add an alpha channel Layer -> Transparency -> Add alpha chanel.
Use the eraser tool and see if you get a checker board pattern.