Graphic converter query - transparency

It's a question I would have thought the manual would help me with, but
it seems not.

Can anyone tell me how to make a (currently white) area around the
outside of an image into a transparent region using Graphic Converter?

(I'm trying to make an HP32E icon for the 32E emulator from here
<http://www.bartosiak.org/nonpareil/index.html>
- scanned in my
calculator, cropped in close, but I'm left with a bit of a border
because the sides are curved and I'd like it transparent)

And while I'm at it: what's the approved method of applying a custom
icon as a one-off in OS X?

I tried the obvious `Get Info' and then found I could paste my prototype
image in if I selected the icon in the top left - but although I gave it
a 128x67 pixel image, what I got ended up much lower resolution than
that and it's all blurry.

Thing is, that's what Mac Help appears to tell me to do.

But it don't work right (bloody bloody grumble moan whine).

Anyone got a hint?

Cheers,
Rowland.

-- 
Remove the animal for email address: rowland.mcdonnell@[EMAIL PROTECTED]
                                            Sorry - the spam got to me
http://www.mag-uk.org
                            http://www.bmf.co.uk
UK biker?   Join MAG and the BMF and stop the Eurocrats banning biking