Cut and attach interior sheathing (plywood)

1: 34-1/2"x24-5/8"x1/2" plywood

1: 65-1/8"x10"x1/2"plywood

Place long strip flush against bottom and leaving a 3/4" overhang off the right edge; this should leave the left edge halfway across outermost stud of window frame

place remaining piece butted up against left edge of tall strip (over the window) and aligned with the tall strip at the top.

There should be a 1.5" overhang along the top

Screw all in @ 16" spacing into all any spanned stud and along perimeter