Introduction:

The past continuous is used to express an action in the past that was in the process of happening.
He was watching TV.

Structure:

subject + was/were + verb + ing
Negative - was /were + not (wasn't, weren't)
subject + was not (wasn't) / were not (weren't) + verb + ing
Interrogative (negative)
Was (Wasn't) / Were (Weren't) + subject + verb + ing?

Examples:

I was talking to the boss when he arrived.
She was not (wasn't) talking to the boss when he arrived.
We were not (weren't) talking to the boss when he arrived.
Was he talking to the boss when he arrived?
Wasn't he talking to the boss when he arrived?