is the white background a perfectly consistent color i.e. white? If it is a photograph, you will need to do a cut-out using the pen tool, else you can just use the magic eraser to cut away the consistent background color.
Mail the pic to me if you want me to have a look at it!
I would use the magic wand and just click on the white area. Depending on the intensity of your wand...just keep adjusting until you find the right balance of what the wand selects...then just hit delete and delete the white.
More than likely you will have to go around the edges of the cut out shape and clean it up a bit. Eraser works well for this.
You can also get into masking which is really the best way to do this...but that's a whole other lesson