Place a nut from the kit over the flanged end of the shorter piece of straight pipe from the kit. Insert a gasket on the pipe in front of the nut with the flanged end of the gasket pointing toward the end of the pipe.
Attach the straight pipe to the drain stub by threading the nut on the straight pipe onto the threads of the stub.
Install another nut and gasket onto the flanged end of the p-trap. The p-trap is the curved piece of pipe. Attach the p-trap to the threaded end of the straight pipe by threading the nut on the p-trap onto the threads of the straight pipe.
Assemble the longer straight piece of pipe with another nut and gasket and attach one end to the other end of the p-trap and the other end to the home's drain pipe in the wall or floor. Tighten all the nuts with a pair of slip-joint pliers, turning the nuts an eighth of a turn past hand-tighten.
Wrap Teflon tape around the threads on the shutoff valves or water lines and the faucet stems. Connect the small fitting on the water supply hoses to the shutoff valves on the hot and cold water lines or to the water lines directly if there are no shutoffs. Hand-tighten the fittings to ensure they are evenly threaded. Snug the fittings with an adjustable wrench.
Attach the large fitting on the end of the hose connected to the hot water shutoff or water line to the hot water faucet stem under the sink. Tighten the fitting with the adjustable wrench after hand-tightening it.
Screw the fitting on the end of the cold water supply hose to the cold water faucet stem under the sink. Hand-tighten the fitting then snug it with the adjustable wrench.
Turn on the water supply by turning the knobs or handles on the shutoff valves counterclockwise. If there are no shutoffs under the sink, turn on the main water shutoff valve for the house.
Turn the fittings on either end of the water supply hoses a quarter turn if there are any drips. Tighten the fittings a quarter turn at a time until the drip stops.