Install the Door Panels
Begin installing your new door. If you're installing a two-car garage door, place a reinforcing bar on the top panel to prevent the door from bowing in the center. Be sure the bar is centered on the panel. Drill pilot holes (Image 1), and secure the bar with screws.
Attach hinges to the top of each panel (Image 2). Many new doors come with pilot holes drilled by the manufacturer.
Attach axle supports to the bottom of the bottom panel and to the top of the top panel.
Place the bottom panel into the door opening. Hold the panel upright by driving a nail into the wall next to the panel and bending it over to hold the panel in place (Image 3). Make sure it's level before attaching the next panel.
Attach the next panel on top of the first one. Make sure the groove of the upper panel rests on the ridge of the lower panel. Repeat the process until all the panels are in place. The final panel should extend 1" or so past the top of the door opening.