Measure the sides, top and bottom edges of the mirror, then cut out pieces of wooden crown moulding to the same measurements using a circular saw. Cut the ends of each section at a 45 degree angle.
Sand the ends of the wooden moulding with medium-grit sandpaper to make the edges smooth.
Paint the moulding pieces using latex paint, then allow the paint to dry for 6 to 8 hours.
Squeeze a line of silicone caulk around the perimeter of the the mirror, then press the wooden moulding pieces in place around the mirror one at a time. Hold each piece in place for two minutes to allow the pieces to adhere to the wall.
Tape the edges of the moulding onto the mirror using paint tape, which will help the pieces stay in place. Allow the moulding to dry onto the wall fr 12 to 24 hours before removing the tape and enjoying your wooden-framed mirror.