Professional Thermal Dye Process
Pull your lenses out of the frame of glasses. You can try dipping them in warm water if they get difficult to pull out of the frame.
Fill the depression of thermal dye unit 2/3rd with lens tint solution. Mostly brown or black colors are used to tint the eyewear lens but you may pick any colour of your choice.
Let the thermal dye unit heat for around half an hour after it is switched on and place each lens in the lens holder.
Now bring the lens out of the thermal dye and let it dry. Remove it from the lens holder after it is dried.
Now fit the lens back into the frame.
Simple Dying Process
Combine the clothing dye and distilled water in a saucepan. You might also require distilled vinegar depending on the clothing dye that you use.
Now boil the clothing dye on your stove and decrease the heat to the lowest minimum possible level.
Place the plastic lens in the simmering dye for a time period between 10 minutes to 1 hour depending upon the intensity of tinting required by you. Light tinting can be done in 10 minutes while dark tinting requires 1 hour.
Pick the lens out of the solution and place it on something (preferably a paper towel) to dry.
Fit the lens back in the frame.