If you've forgotten your username or password (or both), you can reset them in Control Center. If you've forgotten both, reset your username first, then your password. You'll need to know the answers to the security questions you created when you registered as a Control Center user and you'll need to be able to access the email address associated with your Control Center user profile.
If you've forgotten your password and have tried to sign in several times, your user profile may be locked. If this is the case, you can still reset your password, but you'll have to wait thirty minutes for your user profile to be unlocked before trying to sign in again.