Set the countertop face down on sawhorses.
Check the sinks and countertop to make sure the pre-cut openings in the countertop are the right size.
Apply a bead of silicone to the top rim of one undermount sink (Image 1). Set the sink on the countertop and adjust it so it is centered in the opening (Image 2).
Note: Have a helper on hand when setting the sink in place. Ideally, one person should be below the countertop to help guide and center the sink, while the other person works from above.
With the sink in place, position the mounting clips around the edges of the sink. Drill pilot holes, and then secure the clips with the screws provided. Use a stopper on the drill bit -- or put a piece of tape around the bit as a guide -- to avoid drilling all the way through the countertop.
Install the other sink in the same manner
Install a batten board above the vanity to act as a spacer when tiling the wall. If there's a batten board on the wall, remove it before installing the countertop.
Once everything fits perfectly, apply silicone to the top of the vanity cabinet and affix the countertop. Allow the silicone to cure according to the manufacturer's instructions.
Connect the drain lines and overflow pipes to the sinks. If the drains were blocked or covered during renovation, make sure to clear any obstructions before connecting.