Walk to the outside of the home and locate the thin, wooden molding that runs around the perimeter of the sidelight glass. Insert a flexible putty knife between the glass and the molding, then tap the putty knife gently with a hammer to drive the blade under the molding.
Angle the putty knife downward toward the ground and continue tapping it to loosen the entire length of molding. Grasp the molding with your hands and pull it free from the sidelight. Repeat the process to remove the other three pieces of molding in the same manner.
Measure the length and the width of the sidelight glass and take the measurements to a glass supplier to order a replacement piece. Do not remove the glass fully until the replacement piece arrives.
Look at the edge of the sidelight and locate the small metal staples that hold the glass in place. Grasp each of the staples using a pair of needlenose pliers and pull them out. You may want to have another person hold the glass in place as you remove the last staples to prevent it from falling out.
Push the glass from the inside of the home while another person catches it on the outside. Throw away or recycle the old glass and insert the new glass panes into the sidelight.
Insert new metal staples along all four edges of the molding by tapping them in with a hammer.
Apply a thin bead of caulk around the entire perimeter of the glass and replace each of the molding pieces around the sidelight. Tape the molding to the surrounding wall using painter's tape until it dries completely.