You can use a board door lifter to make this easier.
How to hang interior door hinges.
Screw the hinge leaf to the door.
Mount the hinges on the new door and hang the door.
Position one half of a hinge with the inner knuckles in its mortise on the door.
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.
Connect the door to the jamb.
Repeat on the other two hinges.
Slide wedges or shims underneath the door so the hinges line up with the mortises on the frame.
Use wedges or shims to hold the door in the frame at a 90 degree angle.
Follow these instructions to hang a solid core door with minimal effort and a higher degree of accuracy.
If the door is heavy have a partner help you hold it in place.
Hold the door in place using blocks under the bottom to support it if necessary.
If the old door was trimmed at the bottom and you were happy with the gap at the floor cut the new door to match.
Line up the two hinge plates so that the ones on the door match the ones in the jamb.
Keep the door in an open position so you can attach the hinges to the door frame.
While replacing an interior door in an existing opening doesn t require many tools it does require patience and care.
Once you ve finished mortising the hinges set the door upright and bore the lockset holes.
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.