This is a past tense. It is used primarily to describe or set the scene in the past. I will further explain when to use this tense below but first, how to conjugate! The root of the verb (le radical) is found by conjugating a verb in the present tense with "nous" and then removing the "ons". Then you add the imparfait endings (les terminaisons). (For a reminder on what the root and endings of a verb are, visit the page about the Futur Simple).