"She used to eat oranges."
Translation:वह संतरे खाती थी।
The tense form in this sentence is used for regular or habitual events in the past. It has the same construction as the simple present but you replace है/हैं/हूँ/हो with था/थे/थी/थीं. It is not treated as a separate tense in English but talked about using 'used to' or 'would'.
'She ate oranges' would be 'उसने संतरे खाये'. This is in the preterite (simple past) tense and is used for completed events in the past. You'll encounter this tense in the 'Past 2' lesson.