This is an irregular verb. It follows the conjugation pattern of the verb entender.
PresentPresente
La doctora atiende a sus pacientes por la tarde.
The doctor sees her patients in the afternoon.
ImperfectPretérito imperfecto
Mi madre atendía la tienda de la familia.
My mother used to look after the family shop.
FutureFuturo
El camarero atenderá nuestra mesa enseguida.
The waiter will attend to our table right away.
Imperfect SubjunctiveImperfecto de subjuntivo
Le pedí que atendiera a los clientes con paciencia.
I asked him to look after the customers patiently.