If fuiste o fuistes is espanol then it's like this:
Ikimasu (u is almost silent) = go (o ir)
Ikimashita (i is also almost silent and very short in -shita) = past tense of go or went (there is no translation in spanish because there are no general verbs, they are a reduced form of Latin (thankfully) that includes who and verb (i.e. voy, vas, fui, fuistes)
Pronouns are not necessary in Japanese. (I, you, we, he, etc) so there is no need for a subject verb agreement, but you could say it like this:
Anata (you) WA (WA = I just said the subject) ikimashta ka? (Did you go?)
As written, it could be either "fuiste" or "fuisteis". Both are conjugated forms of the verb "ser" in the preterit tense. Fuiste is "you were" singular. Fuisteis is "you were" plural. Both are informal.
Fuiste a ver....
a dónde fuiste mija
adonde fuiste ayer
Fuiste al cine anoche?
Fuiste a la iglesia el domingo?
Fuiste Mala was created on 1999-04-20.
Fuiste Tú was created on 2012-02-07.
yo fuiste a una fiesta en la iglesia
You went to Mass and prayed for me.
No hay mas luz despues que te fuiste
Fuiste mía un verano was created in 1969.