* Early Childhood Education coursework: Many places require additional coursework or a specific certification in early childhood education (ECE) or a related field. This will cover the practical aspects of teaching preschoolers, classroom management, curriculum development, and child safety regulations.
* Teacher training/licensure/certification: Most regions require teachers to be licensed or certified. The specific requirements vary greatly depending on your location (state/province/country). You'll need to research the exact requirements in your area.
In short, a BSc in Psychology is a helpful starting point, but it's not sufficient on its own. You'll need further education and credentials in early childhood education to become a preschool teacher.