Make sure it s flush.
How to hang a door on the wall.
You can use a board door lifter to make this easier.
Finish the corners with a sharp wood chisel.
Cut along the outline down to the sheathing.
Remove door from hinge knuckles.
If the wall is out of plumb and the casing does not rest against it shim behind the casing at the hinge locations to make the door plumb.
If the wall is plumb and the casing rests flush against it tack 8d finish nails through it at the other two hinge locations.
Cut and install the trim on the second side of the door.
With your safety glasses on start the cut with the blade clear of the siding and then lower the moving blade into it.
Working from the hinge side or rear of the door take out the door knob and existing lock set.
Trace the edges of the walls on either side of the door along the back of the board with a pencil.
Remove knob and lock set.
Stop just short of the corners to prevent damaging the siding that will remain.
Lift the internal door out of the clamp offer it up to the frame at a slight angle and screw the top hinge to the lining first.
Put it back against the door.
Nail the trim to the jamb and studs.
Trim door to correct size.
Take the board down and cut along the lines with a circular saw.
How to hang a door in an existing jamb.
Don t fill the hinge up with all the screws yet in case it needs adjusting unless you are hanging a heavy fire check door.