Connect the P-trap to the Drain
Finally, connect the p-trap to the drain by screwing it in place using the threaded connection. Use the threaded fitting to secure the other end of the p-trap to the tailpiece of the drain assembly.
Installing a new vanity sink can cost as much as $1,000 and should take about a day to complete. If you are purchasing a vanity from a home center or local supply house, most will come pretreated with a coating that will protect the top from water damage. If you are retrofitting an antique cabinet, however, you will need to seal the wood around the sink to prevent splashed water from destroying it over time. Water sealers are available at home centers; brush on an even coat, making sure to follow the manufacturer's instructions.
Applying a bead of caulk or sealant around the edge of the sink will help keep water from leaking in around the sink and getting into the finish of the wood, which can rot over time. Apply a caulk bead all the way around the edge of the sink; take a finger and go around the edge, smoothing the sealant down. Don't worry if it's a little messy: a damp sponge will smooth the finish.
When it comes to protecting wood, there is also a protective pour-on polyurethane cover that can be mixed and poured on the countertop. It self-levels. Dry it by gently blowing on it or using a hair dryer.