Attach weather-stripping to the bottom edge of the bottom panel of your metal garage door with galvanized roofing nails, following the manufacturer's instructions. Then, screw cable brackets to the door to secure the weather-stripping, and place this bottom panel in the doorway.
Drive 16 penny nails into the door jamb on each side of the metal garage door to secure the bottom panel. Attach hinges included in your garage door kit to the top edge of the bottom panel; mount the brackets included with your metal garage door kit on the door jambs; and insert rollers into the brackets according to the manufacturer's instructions.
Assemble the vertical tracks for the garage door according to the product manufacturer's guidelines, and stand one track on each side of your garage door. Slip the tracks onto the bottom panel's rollers on both sides, and screw the track to the doorway frame.
Install the rollers into the second garage door panel, place the panel on top of the bottom panel and slip the rollers into the vertical track. Then, attach hinges to the second door panel and attach the second panel to the first panel using hinge screws and a power drill.
Install the third metal garage door panel on top of the second door panel following the guidelines in Step 4. Check to make sure the vertical tracks are parallel to the garage door using a level, and fasten the top plates of the vertical tracks by tightening their lag screws with a ratchet wrench.
Assemble the metal garage door kit's curved and horizontal tracks, following the manufacturer's directions. Connect the vertical and horizontal tracks using the curved corner tracks, and then put the top garage door panel in place following the directions in Step 4.
Screw your metal garage door kit's included rear track hangers to a ceiling joist at both sides of the garage door, and mount the horizontal tracks to the hangers. Attach the springs and lift cable, which also are included in the kit, to the door and hangers according to the manufacturer's instructions.