Creating tension through your lats during the eccentric, or negative portion of the bench is one of the key elements to building a bigger bench.
When you load up properly, it will give you an explosive spring off your chest. I like the analogy of loading up a spring. Press down on the spring as you lower the weight, release the spring and explode up when you press.
Practice this simple bench press drill to build tension in your lats for a bigger bench press: