If you mean you don't have access to the email account, which means you can't receive any emails, then I don't know what you can do.
If you just don't know which of the emails you used, go to the sign up page and keep entering your emails until it says that it's taken.
If you know your username, just use that (given that you have NOT lost access to your email account).
If you have some guesses for your username, go to the sign up page and keep entering your guesses in the username box until it's taken (again, given that you have access to your email account).
Bro I just accidentally deleted my wattpad and I forgot the email I was using I don't even remember the password!!!