What is meant by the term"let the ball get deep on you"?

Hit the ball at the back of the plate. In other words, hit the ball opposite way.

It means keeping your eye on the ball longer as it comes into the strike zone. If you have a short, compact swing, you can see the ball by keeping your head down, watching the ball make contact with the bat and following through. If you have ever heard of "keeping your hands inside the baseball" it kind of means the same thing. You will be able to make better contact and drive the ball where it is pitched, inside to pull and outside to the opposite field.