This is an irregular verb. It follows the conjugation pattern of the verb pedir.
Present:
Ella viste a su hermanita todas las mañanas.
She dresses her little sister every morning.
Preterite:
La madre vistió al bebé rápidamente.
The mother dressed the baby quickly.
Imperfect:
Cuando trabajaba en el teatro, vestía a los actores.
When she worked at the theater, she dressed the actors.