The imperfect tense can be used in French for a description in the past or scene setting for something.
Take the nous form of the verb (eg nous faisons)
Remove the 'ons' part, leaving the stem (eg fais). Add the appropriate ending:
- I - ...ais
- You(singular/informal) - ...ais
- He/She/It - ...ait
- We - ...ions
- You (plural/formal) - ...iez
- They - ...aient
There are a few irregularities, être being the most important, it has the stem ét, making j'étais (I was being) for example.
Verbs with a stem ending in 'g' like manger and ranger have an extra e on the end of the stem (this does not happen when the suffix begins with an i) to soften the 'g' making je mangeais (I was eating) for example. Stems ending in 'c' also get softened making je commençais.