Translation:She used apples to make the jam.
Though technically in English 'marmalade' means a jam like thing made out of citrus fruits. Jam is for non-citrus based ones. It just happens that 'marmellata' is used for both in Italian. So when translating to English, it is best to assume that it is jam unless it is clear there are citrus fruits in it.
To make jam set you need pectin. Apples contain high pectin, so apple can be added to make a strawberry jam set. If you were making blackberry jam, you wouldn't need an apple, because blackberries contain enough pectin. Marmalade is the name given in English to fruit preserves made with citrus fruits.
The answer: "She have used apples to make jam" was incorrect, DL used as correct: "She had used apples to make jam" and "She used apples to make the jam" My question: "ha" is present, not past. In others sentences, like: "Io ho incontrato due dottore" DL correct answer: I have met two doctors "No I'ho mai conosciuta" DL correct answer: No, I have never known her" The auxiliar verb "avere" follow the same tense of the Italian and Enghish sentences. Are there explanations for these differences?