To install a steel door that is attached to a steel frame, create a rough frame for the door that is 1/2 inch wider and 1/4 inch taller than the door. Set the door into the frame, and use a hammer to bend the anchor ties on the door around the jack studs. Check the placement of the door with a level, and make the necessary adjustments before attaching the door to the frame.
To level the door, place a level on the top frame, adjust the door until it is level, and install one screw in the tab on the top of the door frame. Repeat this process with the other three sides of the door, securing each side of the door with a screw. After the door is level and secure, install the remaining studs, attach the clips to the door, and attach the clips to the studs and header with screws.
To install a steel door in an existing opening, check the trimmer to ensure is level, and make the necessary adjustments. Insert four jamb clips into each side of the steel frame, with the top clip 6 inches from the top of the frame and the bottom clip 4 inches from the bottom of the frame, and set the door into the opening. Use a drill and screws to secure the door to the wooden frame.