Remove the old door, trim, and threshold
Measure the rough opening
Check the opening for plumb, level, and square
Repair or shim the framing as needed
Apply flashing tape to the sill and jambs
Install the sill pan or waterproofing membrane
Dry-fit the new exterior door
Place the door into the opening
Center the door and set the bottom on shims
Check the hinge side for plumb
Shim behind the hinge locations
Fasten the hinge-side jamb first
Check the top and latch side for even gaps
Shim the latch side as needed
Fasten the latch-side jamb
Fasten the head jamb
Test the door swing and latch alignment
Adjust shims if the door binds or gaps unevenly
Install insulation around the frame
Seal the exterior with flashing tape and caulk
Install trim and casing
Install the threshold, weatherstripping, and hardware
Paint or finish as needed