If you have more than one email the organiser will only let you in with the email address you used originally so make sure you are putting in the email address that you used when you registered.
Passwords are secure so if you have forgotten your password you need to click on 'forgotten your password' The next screen will ask for your email address. This will send you a random new password. Once you log in with this the first time, make sure you remember to change your password to something more memorable.
But don't worry you can apply do this more than once if you forget your password again.
If you are not getting the new password email make sure it hasn't been caught in your spam folder of your email.