So the thing to keep in mind is that while the liturgy was in Latin, sermons would have been in the vernacular and would have been the ideal time to teach and tell stories to the congregation.

Moreover, priests and also godparents were instructed to teach children the basics of the Christian faith as part of everyday pastoral care.
Too, there would have been visual depictions of bible stories, peoples, and events in the form of murals, mosaics, tapestries, sculptures, etc.

Moreover a wide variety of popular entertainment, from plays to songs to stories were focused on the bible and on religious matters.

The bible was ubiquitous, present across the board in both high and low culture. Keep in mind that only one person in a community need be literate for everyone in that community to have access to that knowledge. Story telling and community gatherings were a part of everyday life in a way that is often hard for us to imagine in modern western society, given that we tend to get our entertainment largely in a private, personal context.