Lay out the two 2-feet long PVC pipes and apply a line of PVC cement around the outsides of the ends of the pipes. Slide an elbow connector on the end of each pipe. Point the elbow connectors in the same directions to create two "U" shaped pipes.
Apply a ring of cement into the inside of the open ports on the elbow connectors, and insert a 1-foot pipe into each elbow connector. Coat the ends of the 1-foot pipes with cement and connect the pipes together with the horizontal points on two T-connectors. Turn the open ports on the T-connectors to the middle of the square. You now have the base for the light post.
Place cement inside the open ports of the T-connectors you just installed, and insert 11-inch pipes into the open connectors. Place cement around the outside edges of the 11-inch pipes, and connect the two pipes together with a T-connector. Make sure the open port of the T-connector is pointing upward.
Slide the 4-foot pipe into the open T-connector port. If the light post is not going to be torn down and packed for camping, you can use the cement to glue the base to the post. Otherwise do not glue the pipes together.
Place glue inside the ports on one T-connector, and slide it on the top of the 4-foot-long pipe. Install the connector so an open port is directly above the 4-foot pipe and an open port is at a 90-degree angle to the 4-foot pipe.
Insert the 18-inch pipe in the 90-degree open port, and place a cap on the end. Slide a 1-foot pipe in the top port.
Line the spike from the solar light up with the middle of the last PVC cap, and trace the outline on the cap with a marker. Cut the outline out with a utility knife, and attach the cap to the top of the light post.
Insert the solar light into the hole in the PVC cap. Apply PVC cement around the base of the light to hold it on.