There's a couple of older threads if you look up 'dying wheels' or something similar.
Pipeous or Timmahh gave most of the answers I think.
Basically ensure the wheels clean and grease free, use an old pot you don't want any more, and on a stove you've no problems if it stains !!!
Bring the water to the boil, stir in the dye, and suspend the wheels / whatever in the boiling dye mix.
The longer you leave it, the more colour it takes in, so time the duration each wheel has.
Whilst it's in the water, turn it from time to time, to avoid surface bubbles, which will limit dying in that area.
Remove, cool, rinse off, there you go.
DON'T FORGET !!! Wear gloves or you could have REAL green fingers, or whatever the colour is !!
Al.