Measure and mark the 1 1/2 inch PVC pipe at 48 inches using a tape measure and pencil. Cut the 1 1/2 inch pipe in half at the pencil mark with a radial arm saw.
Apply PVC primer onto the ends of the two 48 inch pipes and the inside edges of each pipe flange with the included applicator. Apply PVC cement in the same manner over the PVC primer. Slide one PVC pipe flange on each end of the two 48 inch pipes and press the pipe flanges against the pipe ends. The cement will bond the parts together immediately.
Hold one pipe assembly across the top of the alcove opening. Place a level on top of the pipe. Adjust the assembly so that it is level.
Drive wood screws through the mounting holes in the pipe flanges at each end of the pipe into the wall with a screw gun to fasten the assembly to the opening of the alcove.
Slide a stud finder along the wall on each side of the inside of the alcove. Mark the location of the wall stud that is nearest the center of the depth of the alcove on each wall using a pencil.
Position the remaining pipe assembly so that the ends are aligned with the stud markings. Adjust the position of the pipe so that it is level using the same procedure that you did in Step 3. Fasten the pipe to the wall studs at each end using the same procedure that you did in Step 4.
Insert a curtain hook into each slot in the curtain and hang the curtain hooks over the pipe assembly that is installed across the opening of the alcove.