First things first, do you have a tragic back-story? And if so, how tragic is it? Because its too tragic you may be destined to use your powers as a villain rather than a super-hero, ultimately undone by your own hubris and thirst for power.
If you don't have a tragic back-story but still have powers make sure your relatives and other loved ones are safe and not in any danger, especially beloved Uncles and rich parents, use your powers responsibly to help them. Also try not to let your powers BECOME your tragedy as Doctor Bruce Banner did when he became the Hulk, that sad song always plays when he walks away so you know he's a tragic character.
Attempt to discern if your powers are the result of an accident or the product of destiny and also determine if they are caused by naturalistic means or are of a more supernatural bent.
As Rad Man said you might want to see a doctor and confirm that these powers are indeed real and not just the product of an over-active imagination who has seen one too many movies.
DO NOT attempt to fight crime, at least until you've made a badass costume and had a training montage set to snappy music.
But in all seriousness super-powers don't exist and you should probably re-think the whole thing. Want to be a real hero? Do what's right in your everyday life, help people, show compassion and, if still not satisfied, become a member of law enforcement or the military.
Most excellent advice here, but I'd just like to add that if you are thinking about law enforcement or the military please see a doctor first about the super powers thing and please mention them when applying.
How do you find out that you found out? Were you purposely hiding the powers from yourself? Hiding them so well you forgot, or did you find out you found out in an alternate universe. If so, do you have them here or just there? That would be my luck. To be a super hero somewhere else.