When you find out that your child has been sexually abused, naturally you will react emotionally and may be irrational about your next course of action.  Before you approach your child here are some basic tips to follow.  This will ensure you don’t cause more harm to the child;-

You need to create an environment that is conducive for openness and reassurance.  This means getting yourself and the child in a private place where you can both talk about what happened.  Let them talk about it

Though you are angry stay calm and believe every word you child tells you.  More importantly take steps to protect the child from the predator (s) 

Also it will be beneficial to find trusted friends and also go for counselling to help you deal with this situation.  Counselling will help you deal with the pain and more importantly help you be able to minister to the child better