Measure the door opening
Choose the correct door size and swing direction
Remove the old door, trim, and jamb if needed
Check the rough opening for level, plumb, and square
Shim the rough opening as needed
Place the new prehung door into the opening
Center the door in the opening
Shim behind the hinge side first
Secure the hinge side jamb with screws
Check that the door opens and closes properly
Shim the latch side as needed
Secure the latch side jamb with screws
Secure the top jamb with screws
Trim any excess shims
Install the door casing
Fill nail holes and gaps if needed
Install the doorknob and latch hardware
Test the door for proper operation
Adjust hinges or strike plate if necessary