Catechism of the Catholic Church (17.352-410) plays a major role in Antonio's life and in the narrative of the book, but in chapter 17, Anaya lays out specific questions and responses of the Catechism. If you want to learn more about this, you might as well start with what the Vatican has to say on the subject.
La Virgen de Guadalupe (The Virgin of Guadalupe) (4.172-176, 16.43-48): The Virgin is mentioned and prayed to throughout the novel, but the history of la Virgen de Guadalupe is shared in detail twice. You can learn a little more about the story of la Virgen de Guadalupe's appearance at this site.
The People (9.349-351): Samuel drops this Native American legend on Antonio when first talking about the golden carp.
Coronado (4.37): Sure, we'd all love to find a lost City of Gold, but this dude actually got out there and looked for it.