Unscrew the decorative hardware from the cabinets and set it aside in a safe place. Unscrew the hinges and remove the doors from the cabinets. Set the doors on a pair of sawhorses or other flat surface.
Place a piece of coarse sandpaper in your sander. Start with a coarse-grain sandpaper, such as 80-grit, and sand all of the previous finish off of the cabinets. Continue sanding until the surface is perfectly smooth and free of the previous light color. Use a finer-grain sandpaper if necessary to remove the rest of the finish until the entire cabinet is smooth.
Vacuum up any leftover dirt and sawdust from the sanding. Wipe the cabinet clean with a soft cloth.
Lay a drop cloth on your counter to protect it from any drips while you refinish the cabinets. Shake the can of dark wood stain to distribute the color evenly, then insert the paintbrush into the can. Rotate the brush to coat both sides evenly.
Apply the dark stain to the cabinets in the direction of the wood grain. Continue applying the stain until the entire surface of the cabinet is covered. Use a small paintbrush to cover the corners and the area around the door hardware. Be sure the stain is completely dry before replacing the cabinet doors.