Read the explanations and then watch this video.

The verb TO BE is very irregular. This is the past tense:

I WAS
You WERE
He, she, it WAS
We WERE
You WERE
They WERE

I am a waiter I was a waiter
You are in Salamanca today You were in Barcelona yesterday
He is playing tennis He was playing tennis
There is a tree in my garden There was a tree in my garden