Clean the area where you plan to seal with a cloth or paper towel moistened in rubbing alcohol; this will remove any oils, dust and other contaminants that could prevent a good waterproofing seal.  Apply an adhesive (such as silicone caulk) over the affected area using a caulking gun or putty knife.  Spread the water-repelling compound evenly over the adhesive.  Smooth down all surfaces of adhesives with your fingers. Press firmly onto the surface until cured.