Many new faucets require some assembly before mounting to the sink; if that is the case, follow the manufacturer's directions. With most pullout sprayer faucets, the sprayer needs to be threaded through the faucet body first. Insert the rubber gasket between the base plate of the faucet and the sink top to create a watertight seal. If no gasket is provided, pack the cavity of the faucet with plumber's putty, then insert the faucet body through the holes in the sink top. Thread the mounting nuts provided onto the faucet shafts, then center the threaded shafts in the sink's holes and tighten the nuts firmly. Many manufacturers include a special long socket specifically to aid in tightening the mounting nuts. A hole in the socket accepts the shank of a screwdriver, guiding it as you tighten the nuts. If you're mounting the faucet on an installed sink, use this method. If you're installing a pullout sprayer faucet--or a faucet with a separate sprayer--now is the time to connect the sprayer to the faucet body. Check the manufacturer's directions to see if using pipe-wrap tape for this connection is recommended. Use an adjustable wrench to tighten the connection. Most pullout sprayer faucets and faucets with separate sprayers come with a counterweight that attaches to the sprayer hose. This weight helps retract the hose back in to the sink cabinet after you've used the sprayer. Follow the manufacturer's directions on where to secure the weight, and take care not to crimp the hose as you attach the weight. Hook up the faucet's hot and cold supply lines to the water supply shutoff valves under the sink. If necessary, gently bend the copper tubes coming out of the faucet for better access and connect flexible supply tubes to them. Simply wrap a couple of turns of pipe-wrap tape around the threaded nipples on the valves and connect the tubes. Tighten the nuts with an adjustable wrench.