Single dad discovered my 10yr old daughter ing. How do i talk to her about it?

asked her about it she said her friend in the same grade told her about it, told her she shouldnt do it she said it felt good and wanted to know why she shouldnt. told her i would get back with her on the answer to that what do i do now. no female relations to ask for help. student consular said i need to talk to her about it myself. just need some advice from a woman