First of all, it is necessary to identify what role you play in the discussion. Are you a lawyer or legal professional? In such a case, client-attorney privilege means that you can not discuss the information disclosed to you. However, there are certain exceptions to this.
In general, you want to make the young person feel comfortable and confident in talking with you. If they sense that you are going to take further action, they may shy away from speaking with you at all and then end up holding vital information in that can later cause disruption to their sanity and mental well-being. It is important to reassure them that you are there to listen and support them no matter what the case may be.
If they disclose something that you consider morally wrong or even illegal, you may want to suggest in the most sensitive way possible that they discuss their situation with a relevant professional. They may not have the confidence to do so at this stage, so it's important to gently coax them into opening up in order to satisfy the necessary results.
I hope this helps.