Read the directions on the label of the mix before attempting to touch up the furniture.
Using coarse sandpaper, sand and smooth the area you would like to stain. Wipe dust and debris off with a clean cloth.
Apply a small amount of the stain and polyurethane mix to the furniture using a brush or another clean cloth. It is a good idea to only apply it to a small area on the underside of the furniture to first determine if the stain is the correct shade.
Coat the sanded area with the stain and polyurethane mix. Be careful not to use too much. Allow several hours for the mixture to dry.
Sand the stained area using fine-grit sandpaper once the stain is dry. Wipe away the dust with a clean cloth.
Repeat Steps 4 and 5 as many times as needed to reach the desired shade. Normally two or three coats will be enough.