THE PRETERITE TENSE - one off actions in the past - 'to go' (ir), 'to be' (ser) fui: I went, I was fuiste: you went, you were (tú) fue: he went, he was she went, she was it went, it was you went, you were (sing.) fuimos: we went, we were fueron: they went, they were you went, you were (pl.)

SAMPLE SENTENCES
1. Example sentences using 'ir' (to go)
  1. Fui al parque. I went to the park.
  2. Fuiste al parque. You went to the park.
  3. (Él) fue al parque. He went to the park.
  4. Fuimos al parque. We went to the park.
  5. Fueron al parque. They went to the park.
2. Asking questions about one off actions completed in the past - using 'ir' (to go)
  1. ¿Fui al baño? Did I go to the bathroom?
  2. ¿Fuiste al baño? Did you go to the bathroom?
  3. ¿Fue ella al baño? Did she go to the bathroom?
  4. ¿Fuimos nosotros al baño? Did we go to the bathroom?
  5. Fueron ellos al baño? Did the go to the bathroom?
3. Example negative sentences using 'ser' (to be)
  1. No fui yo. It wasn't me
  2. No fuiste tú. It wasn't you.
  3. No fue él. It wasn't him.
  4. No fuimos nosotros. It wasn't us.
  5. No fueron ustedes. It wasn't you. (pl.)
4. Asking questions about one off actions completed in the past - using 'ser' (to be)
  1. ¿Fui yo? Was it me?
  2. ¿Fuiste tú? Was it you?
  3. ¿Fue usted? Was it you?
  4. ¿Fue él? Was it him?
  5. ¿Fuimos nosotros? Was it us?
  6. ¿Fueron ellos? Was it them?