Cut the diffuser sheet so it can be taped to the top frame. Affix the diffuser sheet by duct taping along each edge. You could also use a staple gun. It's important the sheet is stretched tight across the frame ripple free; any sag may hurt your touch-screen and display performance. Next, you will attach the top paneling, which blocks in the plexiglass and keeps it from sliding around. The Plexiglas pane lies unaffixed on top of the frame.