I bought a vanity that was topless

and I have purchased a prefab granite top with undermount sink to put on it. I saved a heck of a lot of money going in this direction $185 for the cherry custom vanity and $100 for the granite top. I just now need to know how to attach it to the top of the vanity. Someone suggested to use liquid nails and I have seen on the home improvement shows to use silicone. which way is the best way?