Here’s the basics of how to install a pedestal sink according to DoItYourself.com:
Prepare the rough plumbing
Shut off the main water supply and drain the hot and cold lines into a bucket. At the sink location, place a bucket under the copper supply lines and, with a compact tubing cutter, shear them both off about 2 inches from the wall. Tighten the cutter slightly after each turn around the tube to avoid distorting the soft copper.
Find the distance from the center of the basin's drain to the wall. (On new sinks, this dimension is supplied with the instructions.) Measure out from the wall and mark this distance on the PVC waste pipe. Hold the P-trap, fitted with its elbow, alongside the pipe, with the trap's vertical end centered on the mark. Now mark the pipe where the PVC shoulder joins the elbow. Using a hacksaw, cut the waste pipe at this mark. To help ensure a square cut, hold the saw parallel to the wall and do not apply downward pressure.
Solder the supply lines
Gently ream the inside edges of the copper supply lines with a pocketknife or the triangular blade on a tubing cutter. This removes the burr left by the tubing cutter. Polish the ends of the supply lines with sandpaper until the copper is shiny. Coat liberally with flux. Polish and flux the inside of the angle stops and slip them, with their escutcheons, over the supply lines. Light the propane torch and apply its bright blue inner flame to the stop, at the spot where the supply line ends.
With your other hand, hold the tip of a length of lead-free solder against the copper tubing where it joins the stop, on the side opposite the flame. When tip of the solder starts to melt, turn off the torch and run the solder around the joint. After it cools slightly, wipe with a damp rag to smooth the exposed solder and remove any flux, which corrodes copper.
Step 3: Install a pop-up drain
Roll a wad of plumber's putty into a ¾-inch-wide sausage and wrap it around the pop-up drain, underneath its flange. Wipe the basin's drain hole clean and drop the pop-up drain through it. On the underside of the basin, slide a gasket and washer onto the drain. Thread the nut onto the drain and hand tighten. Using a wrench or water-pump pliers, finish tightening with a quarter-turn. Set the pedestal on the floor so it lines up with the PVC waste pipe and its center is about the same distance from the wall as the center of the basin's drain (see step 1).
Place the basin on the pedestal and against the wall. Fine-tune the pedestal placement and level the basin side-to-side. Make a mark on the wall through each of the mounting holes at the back of the basin. This shows where to drill later for the lag screws that hold the basin to the wall.
Step 4: Attach the trap
Keeping the pedestal and basin together, move them away from the wall. Have a helper hold the sink steady so it doesn't tip over. Test-fit the P-trap and elbow assembly to the PVC waste pipe, and measure the distance from the floor to the top of the trap's open vertical end. Mark the same distance up from the floor on the tailpiece of the pop-up waste assembly.
Remove the elbow and place the P-trap's slip-nut and washer over the pop-up waste's tailpiece. Cover the P-trap's threads with pipe dope or plumber's tape and slide the trap up to the mark you just made on the tailpiece. Thread the nut on to the trap by hand. Tighten the nut with a wrench or water-pump pliers, taking care not to mar the chrome finish. Drill into the wall at the lag screw locations marked in step 3.
Step 5: Mount the faucet, connect the drain
Place O-rings (if provided) or rings of plumber's putty under the flanges of the faucet's valves and spout, and insert them into their respective holes on the basin deck. Slide a gasket and thread a nut onto the underside of each of the fittings. Tighten the nuts by hand, then finish tightening with a basin wrench. Carefully move the sink back against the wall. Line up the mounting holes in the back of the basin with the holes in the wall. Insert the lag screws with their fender washers through the mounting holes and tighten with a socket wrench while checking for level. Slide on the PVC waste pipe's cover and escutcheon, leaving the plastic exposed.
Test-fit the elbow onto the waste pipe. If the elbow's slip nut threads onto the P-trap, proceed to the next step. If not, there is still some room for adjustment up and down (by loosening the P-trap's nut on the pop-up tailpiece) and front to back (by trimming the PVC waste pipe). When the elbow's nut threads easily onto the P-trap, mark where the end of the elbow touches the waste pipe. Prep the mating PVC surfaces with PVC cleaner, then coat them with welding solvent. Keeping the elbow parallel to the P-trap's mouth, quickly slide the elbow onto the pipe as far as the mark. The weld sets, permanently, in three to five minutes.
Step 6: Make final connections
Place a washer between the elbow and trap, dope the threads, and tighten the nut by hand. Finish tightening with water-pump pliers. Measure the distance between one angle stop and its faucet valve, add an inch, and cut a chromed supply tube to length with a tubing cutter. Slip two compression nuts and a ferrule over the cut end. First, tighten one nut to the stop with a wrench, then bend (don't kink) the supply tube slightly—first to the side, then up—so its acorn head fits into the valve's outlet.
Tighten the head to the valve with the second nut. Repeat for the other angle stop and faucet. With the lift rod in the up, or open, position, attach the pop-up stopper to the actuator arm, then secure the arm to the lift rod with the screw provided. Slide the escutcheon and cover over the PVC waste pipe to hide it. Make sure the faucet valves are closed, then turn main water supply back on. Remove the spout's aerator and filter. Stand to one side and partially open one faucet valve. Let the water run for a minute to clear air and any debris. Repeat with the other valve. With the faucet shut off, check for leaks at all supply connections between the wall and the faucet's valves. Reattach the aerator and filter.