There are many things you will need to do to try and undo what someone else has done.
You will be highly emotional if you find nude photos of yourself online or someone has notified you that there are photos of you on a malicious website. Through your tears - you must, MUST take a screenshot, snap a photo, something that will serve as evidence or all of the above. Your friends or the person who notified you might have already taken a screenshot but it's always good to build your own evidence.
Capture the website url, the date and time it was posted, which is usually at the top of those kinds of posts anyways.
The malicious person who has done the posting can sometimes un-post the nude photos but it's already too late because the internet moves fast. You want to make sure that you have evidence for the authorities and any future lawyer(s) if you plan to pursue legal action.
Please call the police. There is the Canadian C-13 bill that has come into effect as of March 2016. Be prepared to show the police what you have found.
You might already know who has posted your nude photo(s) on the internet. IF there had been a threat from this person to post nude photos online - this should have already been told to the authorities.
If you had not already shared this with the authorities previous to the revenge porn post - share it with the police along with proof of the threat (if you have) such as a text message, an email, a voice mail message, etc.
I cannot guarantee what will happen but in my experience - the police took a lengthy statement and a criminal investigation launched after the new C-13 bill came into effect.
