After installing the drains, the pop up, the faucet and the water supply lines, you can set the sink. Next, attach the supply lines by screwing the nuts onto the feeds from the faucet. Use a second wrench to keep the faucet nuts from breaking off accidentally. The pop-up lever fits through a hole in the back of the faucet. Attach it to the metal strapping under the sink.
Every fixture needs to have a trap.
The basic function of the trap is to keep water contained in the lower curve section, sealing off any sewer gases from coming up the drain line and coming into the house. Careful attention should be paid to the distance between the trap and the drain line. Once the tail piece has been hooked to the bottom of the sink, put on the coupling and the washer, slide them into place, and simply tighten it down to secure the trap. Now you can start connecting hot and cold water lines. First, connect the tub to the waste and vent system.