Used primarily in literary contexts, the trapassato remoto (known in English as the preterite perfect) is a compound tense formed with the passato remoto of the auxiliary verb avere or essere and the past participle of the acting verb. To see how avere and essere conjugate in the remote past tense, see the tables below.
CONJUGATING AVERE IN THE REMOTE PAST
PERSON
SINGULAR
PLURAL
I
(io) ebbi
(noi) avemmo
II
(tu) avesti
(voi) aveste
III
(lui, lei, Lei) ebbe
(loro, Loro) ebbero
CONJUGATING ESSERE IN THE REMOTE PAST
PERSON
SINGULAR
PLURAL
I
(io) fui
(noi) fummo
II
(tu) fosti
(voi) foste
III
(lui, lei, Lei) fu
(loro, Loro) furono
In each sentence set in the trapassato remoto, you will encounter an expression of time, such as the following: appena (scarcely), dopo che (as soon as), or finché non (up until). For example:
Partirono, quando ebbero ricevuto la notizia. (They were leaving when they received the notice.)
Renata entrò, appena Giorgio fu uscito. (Renata entered just after Giorgio had left.)
Andò a casa, quando ebbe finito di lavorare. (He went home when he had finished working.)
From:https://www.dbfei.com/Article/yidaliyu/201311/7711.html