Measure the width between the wall studs. Most building codes require the gap between studs to be 16 inches.
Place the face end of the insulation roll between the metal studs at the top, leaving no gaps between the metal stud framing and insulation.
Unroll the insulation downward to fill the cavity between the metal studs. Press the insulation so it rests snugly between the studs.
Using a utility knife, cut off excess insulation that does not fit between the studs.
Custom-cut insulation pieces to fill any gaps between the studs. Areas to fill may include the perimeter of electrical outlets and small gaps around doors and windows.