Final answer:
To install a prehung interior door with casing attached, follow these steps.
Step-by-step explanation:
To install a prehung interior door with casing attached, follow these steps:
- First, measure the rough opening to ensure the door will fit properly.
 - Remove any existing door and frame from the opening.
 - Position the prehung door in the opening and secure it with shims.
 - Ensure the door is level and plumb.
 - Secure the door in place by driving screws into the door frame.
 - Attach the strike plate and test the door to ensure it opens and closes smoothly.
 - Finish the installation by adding trim and casing around the door.