Ils/elles avaient regardé= They had watched.Il/elle/on avait regardé= He/she/it had watched.We use the same past participle as we do for “le passé compose.” We can pick ”regardé” and ”parti” to serve as examples. In the imperfect tense, do you remember the conjugation of ”avoir” and ”être”? We need to use ”avoir” and ”être” to create the basic form of this tense.