To express was.
When talking about action in the past, use the imperfect indicative tense of estar –> estava.
estar
to be
euestava
você, eleestava
nósestávamos
vocês, elesestavam
Eu estava almoçando quando você ligou. ➜ I was having lunch when you called.
Ela estava ocupada ontem. ➜ She was busy yesterday.
*Don’t use this to express was for talking about permanent things in the past (I was a young boy; She was a sick baby etc.) – use ser for that.