You can't, really, do that very easily. It's someone else signing up using your information, or rather, they've breached your data. The best way to protect yourself when you get breach notifications is changing all your passwords on your accounts (at least, the passwords that were breached), that's the purpose of the notification.

Hi, I have the same problem. I am informed that there is a data breach on an account that is not mine. I tried to login using my email address. Of course, I did not have a password. I did not receive an reset password email. So I don't think there is an account. Is this data breach resolved? Is there anything else I can do? Thanks, Andrea