Reflexive verbs always use reflexive pronouns in the preterit, as shown below. They always appear immediately before the conjugated verb, as they do in the present tense and all other tenses.
means to wash oneself. It is a reflexive verb, since you do it to yourself, it it is lavar, means to wash somebody and therefore, not anymore a reflexive verb.
The reflexive always need from a pronoun.
I order to remember see THIS CHAPTER of Spanish pronouns
Pronoun Verb conjugated Stem Ending
(Yo) me lavé lav é
(Tu) te lavaste lav aste
(el/ella) se lavó lav ó
(usted) se lavó lav ó
(ustedes) se lavaron lav aron
(nosotros) nos lavamos lav amos
(ellos/ellas) se lavaron lav aron
Hace (from the verb hacer / to do, to make may be used with the preterit tense to mean ago, like the following examples.
Construí la casa hace dos años. / I built the house two years ago.
Estudié esa lección hace dos semanas. / I studied that lesson two weeks ago.
Certain adverbial expressions of time are often used with the preterit tense. The following is a list of some of the more common ones.
anoche / last night
ayer / yesterday
anteayer / day before yesterday