I used the wrong email address to sign up. How can I solve this problem ?

The procedure to solve the problem depends on the moment you noticed it. 

Indeed, when you validate your registration, a pop-up window indicates that you will receive a confirmation e-mail and asks you to validate that the e-mail address is correct. You can change it at this moment. 

If you only notice it later, you will have to inform the customer support by email or by phone.