If your wheels are polished finish now, painting them is easy.
Get your self some painters tape, and some sand paper, and do yourself a favor and use Dupli Color's wheel paint, assuming you are going to rattle can them. The Duplicolor cans spray very even, and the paint holds up very well.
Sand the spokes, or the surfaces you are going to be applying paint. Clean the surface, tape off the areas not to be painted, and start with Dupli colors primer. Then follow with thin even coats of the color.
They'll hold well, here's an old Road Runner of mine I painted with their black.
Guy who bought it is local, and he says they still look great after 3 years!