Installing the hinges (now remove the old ones from the old Door) use them-

as a pattern for the new door this is the critical step and using the old hinges as patterns is smart . Lay the old top hinge on the edge of the new door making sure the distance from the edge is exactly the same as the old door! Now measure the distance down from the top of the old door . then trace the hinge. Repeat for bottom hinge.

Match the depth of the original cut out on the old door . Basically you want the hinge flush with the door .Cut out the new hinge carefully with a nice sharp chisel 1-incher is good must be sharp. Repeat for the bottom hinge . You can buy new hinges or clean up the old ones and reuse them if there ok and screws aren't stripped.