"Se lo di"The first part of this translation is choosing the correct verb, dar, and correctly conjugating it into the appropriate past tense (in this case the preterite, as it is an action that was done once and completed). The other parts are selecting the correct pronouns to represent "it" and "to him".This requires an understanding of Direct and Indirect objects and their pronouns. The direct object pronoun in this case is "lo", so to translate "I gave it" you would say "lo di". The indirect object pronoun is "le", so to translate I gave to him you would have "le di". Combining them requires one more thing - there is a rule in Spanish that we cannot say "le lo di", and in this case the le is changed to se for reasons of pronunciation. This is how we end up at the final answer.