Wenn du sagen willst, dass etwas bereits vor einem Zeitpunkt in der Vergangenheit stattgefunden hat, verwendest du das past perfect (Plusquamperfekt, Vorvergangenheit).
When I arrivedSue had already gone home. Mike was late becausehed missed his bus. Ann wanted some cakeafter Id washed the dishes. geschah in der Vergangenheit: simple past geschah noch davor: past perfect
I arrived at the party at 9 oclock. When I arrived, Sue had already gone home. Mike was late for school yesterday. Mike was late because he had missed his bus. Ann had some cake this afternoon. Anne had some cake after I had washed the dishes.
.. I arrived at the party.Sue went home. 9 oclock8 oclock
.. I arrived at the party.Sue went home. When I arrived, Sue had already gone home. 9 oclock8 oclock
In Nebensätzen mit after (= nachdem) steht oft simple past statt past perfect, weil eindeutig ist, in welcher Reihenfolge die Handlungen oder Ereignisse stattgefunden haben:
Ann wanted some cake after I washed the dishes.
Das past perfect wird mit had (Kurzform: `d) + Partizip Perfekt gebildet. English G 2000 3 Unit 6; Cornelsen Verlag, Berlin, 1998 (2001), Seite 126