Username is your e-mail address you entered on registration. If you have forgotten your password, enter your e-mail address and click on Password?
Password? option is under the login field in the upper right corner of the web site.
After you have clicked on Password? a short form will appear that you should fill with: your e-mail address and security question.
An e-mail with the link on password reset verification shall arrive to your e-mail address. Click on the link immediately upon the reception of the e-mail because the link is limited in time. You will receive a temporary password. When you login using that password the site will require the change of the password. enter the temporary password in the old password field, and the password you plan to use in the future in the new password field.