"How to Say the Rosary" is a book that provides instruction on how to pray the rosary, a popular devotional prayer in the Catholic Church. The rosary is a set of prayer beads that consists of a chain of five decades, each decade representing one of the mysteries of the Rosary. Each decade is divided into ten smaller prayers called "Hail Marys," which are recited while meditating on the mysteries of the rosary. The book "How to Say the Rosary" would likely provide a step-by-step guide on how to pray the rosary, including the specific prayers to be recited and the mysteries to be meditated on during each decade. It may also offer explanations of the symbolism and significance of the rosary, as well as tips for making the most of this spiritual practice.