There is no problem if you've forgotten your login details.
If the website claims that you have forgotten your password when you try to login you can use this link to reset your password.
An e-mail link will be sent to the e-mail you registered.
Please note that, it can take up to 30 minutes before you recieve the e-mail. And that it could end up in your spam folder, so make sure you check there.
Your username is the e-mail you used when you created your account.
If you created your account via Facebook, then your username is the e-mail that is connected to your Facebook account.
If you after all this still can't login, please send us an e-mail at email@example.com and we will help you.