How is the perfect tense formed with avoir?

The perfect tense is used to describe a one-off action which occurred in the past. It requires three components: SUBJECT (je/tu/il/elle/on/nous/vous/ils/elles) + AUXILIARY (present tense form of avoir) + PAST PARTICIPLE.

The AUXILIARY is the present tense form of avoir: J'ai Tu as Il/elle/on a Nous avons Vous avez Ils/elles ont

The PAST PARTICIPLE is the past tense form of the verb that you want to use. To form the PAST PARTICIPLE, you have to take the infinitive (full) form of the verb and remove the -er, -ir or -re endings. For -er verbs, you replace the ending with 'é'. For -ir verbs, you replace the ending with 'i'. And for -re verbs, you replace the ending wth 'u'.

FOR EXAMPLE, if I wanted to say 'I ate', I would take the SUBJECT as 'Je', the AUXILIARY as 'ai' and the PAST PARTICIPLE as 'mangé'. The full phrase is 'J'ai mangé.

Other examples include: J'ai choisi - I chose Il a vendu - He sold Nous avons acheté - We bought