Past simple (summary)
The past simple (also called past indefinite) is the basic and the most commonly used past tense. We use the past simple to talk about actions that happened and completed in the past. With the past simple, we normally use such indicators of time as X days ago, last year/ month/week, yesterday, in 2007 etc.
To form the past simple we add -ed to the main verb or put it into the second form if it is an irregular verb. To build questions and negatives we use the auxiliary verb did/didn't. In this case, the indication of the past simple goes to "did/didn't", instead of the main verb, so the main verb returns to its infinitive form.
The verb to be becomes was/were in the past simple:
You can read more on how to form and how to use the past continuous in the related topics.