These new challenges are placed in Secret Chapters. If you didn't already find Secret Chapters in-game, you will have to locate them first to access the new challenges. There are two new challenges per World and we are introducing a new difficulty: Ultra Hard.
We are also including 5 New Co-Op Challenges. They can be found at the Buddy Dome in the Peach Castle area.
For more information about Co-Op Challenges, check out the article HERE.