Locate the studs in the wall where you will install the vanity, and mark their locations with the pencil. Use a carpenter's level to make sure the marks are level.
Drill a hole into each stud at the desired height for the vanity. Use a drill bit one size smaller than the mounting screws included with the the hanger for the wall vanity.
Screw the two mounting screws through the hanger cleats into the drilled holes so the top portion of the hanger cleats points toward the ceiling.
Check the level of the vanity again with a carpenter's level placed across the two hanger cleats.
Place the wall vanity against the wall slightly higher than the cleats. Slowly lower the vanity until it rests on the cleats.