A silicone removal tool, then stanley to get the hard to reach bits.
Then use silicone remover to get the remnants off, followed by a good wipe down with rubbing alcohol or meths to clean the joint.
Apply some good silicone (dow corning 785 is king).
Cut the nozzle at an angle, apply a thin bead and smooth with (preferably) a wet fugenboy tool, or a finger and some washing up liquid.