Answer:
El domingo pasado, mi novia, Marcela, y yo fuimos al centro comercial a comprar ropa. Nosotros (1) llegamos a las nueve y media de la mañana, pero ese día el centro no (2) abría hasta las diez. Entonces, nosotros (3) esperamos en una cafetería cerca del centro. A las diez en punto, nosotros (4) empezamos a visitar las tiendas. Primero, Marcela (5) compró un traje muy bonito. Después, un dependiente me (6) mostró una chaqueta muy elegante, pero demasiado corta para mí. Al fin, yo (7) encontré una tienda de ropa con tallas para personas altas. Yo (8) vi unos pantalones perfectos y otras cosas que necesitaba. Nosotros no (9) salimos de la tienda hasta que los dependientes la (10) cerraron.
Explanation:
This text is talking about an action in the past, that's why it's in the simple past which is called pretérito indefinido o pretérito perfecto. All the verbs are in the preterite except "abría" (2) which is in the imperfect because it implies that they would have to wait until 10. However, it could be conjugated in the preterite and still be correct although the meaning wouldn't be exactly the same but it'd still be grammatically correct.
To conjugate the verbs in the preterite, you have to determine its infinitive and after that change the ending of the verb. For example, when verbs end in -ar the preterite of the first person plural ends in -amos:
(1) llegamos: the infinitive is llegar
(3) esperamos: the infinitive is esperar
(4) empezamos: the infinitive is empezar
The first person of -ar verbs is formed by -é:
(7) encontré: the infinitive is encontrar
The preterite of the third person singular of verbs ending in -ar is formed by ó:
(5) compró: the infinitive is comprar
(6) mostró: the infinitive is mostrar
The preterite of the third person plural of verbs ending in -ar is formed by -aron:
(10) cerraron: the infinitive is cerrar
Verbs ending with -er and -ir share the same ending in the preterite. The preterite of the first person of verbs ending in -er or -ir is formed by -i
(8) vi: the infinitive is ver
The preterite of the third person of the plural of verbs ending in -er or -ir is formed by -imos
(9) salimos: the infinitive is salir
