The use of the preterite tense in Spanish does not differ too much from the use of the past simple tense in English.

As usual, Spanish has 3 infinitive endings in -ar, -er and -ir from which different forms of the preterie derive. Verbs ending in -ar make the preterite ending in -é, -aste, -ó, -amos, -asteis, -aron (as in the verb andar "walk": ande, andaste, ando, andamos, andaste, andaron) whereas verbs ending in -er form the preterite ending in -í, -iste, -ió, -imos, -isteis, -ieron (as in the verb comer "eat": comi, comiste comio, comimos, comisteis, comieron).

The preterite is used to refer to finished actions in the past, as if you were trying to narrate a story in which one event happened after another. A good trick is to think o the actions as if you were moving clockwise.