Use tools like the IWF to have the images removed. They work with tech companies to take down child sexual abuse imagery (CSAI).
A clear description of the image and the person in it.
(If you are the victim or reporting on behalf of a minor).
When reporting the sharing or possession of nude or semi-nude images involving teenagers (under 18), it is crucial to handle the situation with care to protect the minor, focusing on removal and legal reporting rather than punishment.
Advice on kids sending inappropriate images at school : r/Teachers
Take screenshots of the message, sender's profile name, date, time, and URL where the content is posted.
Provide direct links to where the image is publicly displayed.
In the U.S., report to NCMEC’s CyberTipline .