You DO NOT want to do this manually... or really atall because of the dangers of creating a system that fails to boot.
However it is doable, so I suggest you get a utility to help you.
http://www.computa.co.uk/staff/dan/?p=18
It isn't 64bit compatible and none will be until they figure out a way to add to the kernel.
Just give that utility a bitmap and it will make you a boot screen!
crabby