You should apply exterior caulking to seal against drafts. It also prevents moisture from entering your home and keeps heated or air-conditioned air inside. Properly caulking helps keep your house weather-tight, lowers heating and cooling bills, and prevents damage to structural elements. You should also caulk before painting with a paintable caulk, as it eliminates edges where the paint may start to peel and creates a better edge.
Be sure that you exercise care on ladders and follow the precautions and warnings on your ladder.