Have the plumbing run to the location if the shower unit is being installed where none existed previously. The plumbing work should be done by a qualified professional. Be sure to gain a permit before the work is done and a passing inspection after completion.
Prepare and area where there is an existing tub or shower that is being replaced. Turn off the water, disconnect all the plumbing fixtures and remove the previous occupant of the location. Clean out any debris. Set the fixtures aside if you are going to reuse them and they fit the new unit.
Set the shower drain pan in place. For a new install, note the location of the drain hole, and mark this on the floor by tracing the inside of the drain hole. Use a hole saw bit in the matching size to cut the hole out in the floor to access the drain line that has been installed for the shower unit. For an existing location, the drain line should line up with the hole in the pan. If it does not, cut a new hole.
Assemble the drain unit and connect it dry to the drain line that was installed for the shower. The drain unit consists of a p trap, or a curved piece that dips down from the shower drain to the drain line, attached to a drain screen that sits on the shower floor. The screen keeps debris out of the lines and the p trap keeps odors from coming back up into the room. Cut or extend the drain line for an existing location that is in a new hole. Add an extension of PVC pipe and glue in place to meet the new length, or use the hand saw to reduce the pipe already in place.
Measure the hot and cold water lines for a new installed location. Measure from the floor up to both the location of the fixture handle and the shower head. Transfer these measurements to the panel of the shower unit that will sit on the wall where the fixtures are located. Double check to make sure your measures are correct; the shower unit will be ruined if they are wrong.
Cut the holes with the hole saw bit and drill, using the size bit that is large enough to accommodate the diameter of your plumbing lines and a 1/4 inch allowance for movement.
Check the walls for level. Line up the drain to the shower base and assemble it. Set the shower base in place, and glue the drain plumbing assembly together with the PVC glue. Use the construction adhesive to attach the shower base, and consult the manufacturer's instructions for any specific requirements. Check for level and shim the base if necessary to adjust it. Weigh the base down with bricks or weights until the adhesive dries.
Install the double-sided foam tape strips to the edges of the panels, leaving the outer tape that will adhere to the wall in place until you install them. Make sure you use the tape to run a seal along all the outer edges of the shower and wherever the manufacturer recommends.
Apply adhesive to the panels. Remove the covering paper from the foam seal tape and set the shower unit in place, making sure the lip at the bottom is over the shower base.
Caulk the seams of the entire unit after the adhesive has been given time to dry, and remove the weights from the shower base. Re-attach the fixtures or install the new ones, and test the drain to make sure it is not leaking.