Cut out the main section of the building. Be careful when scoring the folds not to score across the tower. Fold the walls around on the dotted lines and glue the rooftops down to the flaps to make three walls with square corners.
Cut out the rear interior wall of the building, score and fold it into shape. Place the rear wall in position behind the front wall. It is easiest to position the rear wall if you only glue the sides of the tower and the nearby wall at first (as shown in next diagram). With the top of the tower open you will be able to adjust the position of the walls of the tower to match the pieces perfectly.
After the tower is straight and square you can fold down the flaps and roof on top. Then glue the left and right ends of the rear interior wall to match up with the roof line of the building.
Cut out the roof of the theater and fold it into a stair-step shape with flaps folded down. Glue this inside the interior wall of the building as marked in yellow.
Aha! There is a mistake on the postcard model. The flap marked in red should be cut off from the rear exterior wall.
Fold the rear exterior wall with a little zigzag in the middle to match the shape of the theater rooftop piece. Glue the exterior wall to the model carefully, tucking the flaps on top under the top roof of the building and adjusting the fit quickly before the glue dries.
Cut out and fold the small pieces remaining on the postcard. The low rooftop building covers the upper galleries of the theater inside.
The squarish piece is a banquet hall perched above the arched ceiling of the theater, high above the main seating area. The angled wall of the banquet hall should face the exterior rear wall so that the tiny fire escape ladders match up.
Finally, add the boxy structure that houses the stage machinery.