Presente
Passado
I am (Eu sou/estou)
I was (Eu era/fui/estava)
You are (Você é/está)
You were (Você era/foi/estava)
He is (Ele é/está)
He was (Ele era/foi/estava)
She is (Ela é/está)
She was (Ela era/foi/estava)
It is (“Isto” é/está)
It was (“Isto” era/foi/estava)
We are (Nós somos/estamos)
We were (Nós éramos/fomos/estávamos)
You are (Vocês são/estão)
You were (Vocês eram/foram/estavam)
They are (Eles são/estão)
They were (Eles eram/foram/estavam)

Vamos dar uma olhada em alguns exemplos:
I was a teacher. – Eu era/fui professor.
I was 25 years old at that time. – Eu tinha 25 anos naquela época/tempo. (Lembre-se de que usamos o verbo ser/estar para falar que temos 25 anos. Fica estranho, pois se traduzirmos ao pé da letra a frase seria “Eu era/estava 25 anos”, mas é assim mesmo que se fala!)
I was there. – Eu estava lá
I was at home. – Eu estava em casa.
You were happy. – Você estava feliz.
You were a student. – Você era/foi um estudante.
You were at the station. – Você estava na estação.
He was my friend. – Ele era meu amigo.
He was an engineer. – Ele era um engenheiro.
He was there. – Ele estava lá.
She was my girlfriend. – Ela era/foi minha namorada.
She was a teacher. – Ela era/foi professora.
She was working. – Ela estava trabalhando.
It was a computer. – Era um computador
It was there. – Estava lá.
It was a good game. – Foi um bom jogo
We were students. – Nós éramos/fomos estudantes.
We were studying English. – Nós estávamos