To tighten the nut, locate the bolt on the sink cabinet's roof. Make sure to use a wrench with the appropriate size. Tighten it clockwise until the nut can no longer move. Once the nut is tightened, make sure to check the faucet for leaks. If it's not tight, you may need to call a plumber. It's important to know how to properly tighten the faucet https://www.nivito.com before you try to replace it.