How do you install a new door in an existing door frame?

You'll have to go back down the door and shave some of the material with a manual planer until the door opens and closes freely. Replace the old door over the new one, and then transfer the hinge shroud, the shrouds of the lock set, and the contours of the door holes. Once the door is properly adjusted, you can reinsert the remaining hinge bolts and install any other decorative accessories or door stoppers.