Answer:
You would use the verb "ir/ser" since they already went to the beach (ayer= yesterday). So, the conjugation would be: Fuimos. ( the subject "yo" is included in the action)
Explanation:
Susana, Mateo y yo (nosotros) fuimos a la playa ayer.=
Susan, Mateo and I (we) went to the beach yesterday.
Ir/Ser (irregular preterite)= fui, fuiste, fue, fuimos, fueron.
I hope this helps you! :)))
