Fill - if there is any scars, cracks, curbs etc, fill them with soemthing, body filler should be ok, wont last forever though.
Sand it down
Spray the wheels in primer (this is basically a surface to bond between the wheels and the paint.
Spray the wheels in paint, colour of your choice
Lacquer them if the paint requires it.
Someone could probably add a little more detail on than me, i'm just half asleep.