Forcing turnovers refers to your players stealing the ball from the opposing teams players. With whole pitch pressing, you'll be defending on the opponents half of the pitch, so those turnovers will result in possession deep in the opponents half for you.

I can't recall the exact formation I used to beat this formation (it was 7 seasons ago in the 3rd round of the cup), but it was some form of 3-5-2 or 3-4-3!