Use a putty knife or 5-in-1 tool to pry the old caulk out of the joint.
Cut the tip of the caulk tube at a 45-degree angle. Puncture the inner seal. Insert the tube into the caulk gun. Hold the gun at a steady angle and pull it toward you, forcing caulk into the gap. Aim for a bead about ¼ inch thick. how to reseal a window fixed