You'll need to establish that superpowers are part of your world early on.
Whether it's magical realism, urban fantasy, or comic book standards, your novel needs to set the framework within the first few chapters.
If you're showing other superpowered folks up front and just not revealing that your MC has this in common with them, then you can take longer to reveal the truth.
If the existence of the other superpowers isn't part of the early story, then have your MC uncover the truth with the reader. Did s/he lift something exceptionally heavy, or not get a scratch after a fall from a bicycle. Or maybe s/he thinks she's going crazy hearing other people's thoughts. Something related to her/his eventual power.
When you reveal it depends a lot on your story and genre. If other superpowered people are active in the story, then it may seem odd to withhold your MC's powers. Or it could work, it just depends. If your story is more straight forward literature and the fantasy elements are there but subtle, then the revelation could come late in the story.
The standard method would be to have the MC suspect something is up and go looking for more information. Then the reader experiences the journey with her/him.
If you want to emphasize the journey, reveal everything late. If you want your MC spend time using powers, then reveal things fairly early. If you want a balance, place the reveal in the middle.