Question

Como se usa o there was e o there were?

Answer 1

É simples, a forma verbal "There to be" tem o significado de haver, de existir ou ter, em português, no presente.
O "There to be" tem duas formas - o "there is" e o "there are"..a primeira no presente do singular, a segunda no presente do plural.

Da mesma maneira, no passado, temos as formas "There was"e "There were"..no singular e no passado.

Ex.: There is a car in the street (Há um carro na rua)
       There was a car in the street (havia um carro na rua)

     There is someone waiting for you (Há alguém esperando por vc)
     There was someone waiting for you (Havia alguém esperando por vc)

     There were different kind of food (Existiam diferentes tipos de comida)
     There were 40 people at the party (Havia 40 pessoas na festa)
     There were a lot of messages from Susan on my answering machine (Havia um monte de mensagens da Susan no meu atendedor de chamadas)

Answer 2

there was- vc usa no singular
there were- vc usa no plural