Fit the strainer that came with your pan to its drain hole. Most strainers consist of two pieces that screw together with a watertight rubber seal in between. The top of the strainer must be slotted through your pan's drain hole and screwed into its bottom section.
Put on your tiler's gloves and knee pads. Then, lower your shower pan into position. Ask an assistant to help you if the pan you're working with is very large or heavy.
Knock the pan into place in your shower cubicle with a tiler's mallet. Then, adjust your pan's feet so as it's level. Use a bubble level to make sure it's not fitted at an angle. If your pan doesn't have adjustable feet and your're working with an even wooden subfloor, nail shims into your floor to create a level base. If you're working with a concrete subfloor, lay a self-leveling cement with a trowel.
Connect the trap beneath your pan to the bottom section of the strainer fitted to the underside of your pan's floor. This will screw into place. Secure the connection with a bead of tiler's silicone sealant.
Apply silicone sealant to the joints between your shower cubicle's walls and the top of your pan. Use silicone smoothing rubber tools to create a clean finish.
Replace your pan's detachable side if it has one.