How Do I Change a Perfect Active to a Perfect Passive Form?
(Cf. Wheelock 19)

1. Start with the perfect active form that you wish to change. AMÂVÎ
I have loved
I had loved
I will have loved


2. Get the FOURTH principal part, and give it the correct gender and number, according to the subject. AMÂTUS loved
3. Add the appropriate form of esse, according to tense and according to the number and gender of the subject. AMÂTUS SUM
I have been loved
I had been loved
I will have been loved

Further Examples:

The girls have been reminded. Puellae monitae sunt.
The towns will have been taken. Oppida capta erunt.
The speakers had been heard. Ôrâtôrês audîtî erant.
The books were sent. Librî missî sunt.
The book was sent. Liber missus est.