Work the tub into place. Be careful not to damage the drain when repositioning the tub. Check to make sure that the drain lines up properly into the hole.
Use a 1/8" drill bit to make a pilot hole through the tub into the stud. Drill into at least two studs on each side of the unit. Then use a Phillips head screwdriver to attach a 1-1/2" weatherproof drywall screw into each hole. Hand tighten only – don't over tighten or you could crack the tub.
Install the P-trap onto the tailpiece and hand-tighten the compression nut. Using a PVC pipe cutter cut the existing drain line to size. Then, clean and cement the 45-degree PVC fittings you need so that the P-trap will be near the drain line.
Install the assembly onto the home's drain line.
Now you need to extend the water lines to stub them out under the tub. Cut and solder lengths of pipe to get your water lines just below the holes you made under the tub and use a 90 and a 4" piece of pipe so that it can come up into the bathroom. Use a board or pipe straps to hold the pipes in place.
Continue soldering until you tie into the water line.
Now, go back into the bathroom and use a pipe cutter to cut the stubbed pipes to length. Then, solder a threaded male adaptor onto each pipe.
Your next step before you can move onto the finish and trim work is to do what's called securing the pump. During shipping the pump is tied up so it won't fall all over the place. So after you get the tub in place you have to lower the pump, screw it into place and that way your whirlpool will run quietly.
Using 'A' snips, cut the two straps that hold up the pump. Then, do the best job you can to screw the pump to the sub-floor.
Attach the spout and handles as per your manufacturer’s instructions.
Next, place the drain plug assembly into the drain hole. Then, install the trip lever assembly into the overflow drain hole and screw it into place. Finally, install the knob according to the manufacturer's instructions.