This tense is often used with the following time expressions:
... when xyz happened
... while xyz was happening.
Subject + was / were + verb + ing + object(s) + time Expression
Sharon was watching TV when she received the telephone call.
Subject + was / were + not (wasn't, weren't) + verb + ing + object(s) + time Expression
We weren't doing anything important when you arrived.
(Question Word) + was / were + subject + verb + ing + object(s) + time Expression
What were you doing when Tom gave you the bad news?
Take this past simple quiz to check your understanding.
If you are a teacher, use this guide on how to teach the past simple tense for more help.