Here are the steps to install exterior trim around a window: ^{finehomebuilding.com 3 1 2 4}

1. Use a utility knife to score through the dry paint into the drywall along the seam between the moulding and wall.
2. Insert a pry bar into between the trim and wall, and pry the trim from the wall.
3. Repeat step 2 for the opposite side trim and upper and lower trims.
4. Pre-drill nail holes in the trim, then nail the trim to the wall.
5. Apply caulk around the trim.
6. Fill the nail holes with painter’s putty.
7. Prime and paint the trim as needed.