Each World Star is comprised of Bingo Chapters, with each chapter made up of nine Bingo Pieces.
The Bingo Pieces can be acquired as a Homerun Ball Reward or a reward from a Chest item.
You may also acquire them by completing a line of Bingo or completing the Bingo board.
A Bingo Chapter unlocks when a player unlocks a stadium.
(e.g. Bingo Chapter 2 unlocks when a player unlocks Stadium 2.)

Acquired duplicate pieces are converted into Stars.
Acquired Stars can be exchanged for items at the Star Exchange Center.