Select a level, flat part of your yard to place the pool. Avoid areas with large rock outcroppings or mazes of tree roots. Measure out the 18-by-33-foot area of the pool, and mark the boundaries using chalk or spray paint.
Remove the top soil and grass inside the boundaries of the pool. Visually inspect the area for any lingering rocks or tree roots, and use a rake to spread 2 to 3 inches of sand evenly throughout the hole. This creates a soft, sandy bottom for the pool.
Connect the horizontal supports using the manufacturer-recommended bolts for the pool to create the pool frame. Dig a hole 5 inches wide and 2 inches deep for each support, and place the supports in the ground. If the ground is soft, place a concrete block in the hole first to prevent the pool from shifting or collapsing.
Attach the tension straps to each side of the horizontal supports and connect the straps in the center of the pool. Snap the bottom rail pieces together and set them in the frame, bolting them in place as necessary.
Set the pool wall material in place in the bottom rail and secure it to the frame using bolts. Face the heads of the bolts toward the inside of the pool to avoid accidental punctures of the liner and potential cuts to bathers.
Build a mound of sand 6 to 8 inches high around the inside of the pool wall. This holds the liner in place and prevents slipping. Back fill the holes for the pool supports using soil.
Open the liner and spread it out inside the pool on top of the sand. Drape the liner over the pool walls, allowing it to hang down several inches. As water is added, the liner will be pulled inward so extra liner space is provided. Secure the liner with liner clips, and place the top rail pieces over the edges of the pool.
Begin filling the pool with water. As the pool fills, watch to make sure the structure remains steady. Adjust the liner if necessary to prevent tearing.