the first thing you must do is sand down the cabinets to get rid of the sealer and then you can buy the color of stain that you want and then apply it to your cabinets to your standards. apply 2 or 3 coats and then reapply a clear sealer to your cabinets
The easiest suggestion would be to sand and paint the cabinets. Sand them down to the bare wood, primer them, and then paint in a semi-gloss dark paint.