Question

Como se usa WAS E WER?

Answer 1

são os verbos to be no passado, was-singular were-plural

Answer 2

Was/Were, equivalente ao verbo to be no passado, são utilizados assim:

PRONOME      VERBO TO BE NO PASSADO (Afirmativo, Negativo)
I                      Was    Was not/Wasn't
You                 Were    Were not/ Weren't
He                   Was    Was not/Wasn't
She                 Was    Was not/Wasn't
It                     Was    Was not/Wasn't
We                  Were    Were not/ Weren't
You                  Were    Were not/ Weren't
They                Was    Was not/Wasn't

Veja também a tabelinha em anexo que explica melhor. Espero ter ajudado e bons estudos ;)