Input data only to fields User and Password of the web-phone.
Information about your login/password you get to your e-mail after successfull sign-up. Also you can renew this information by loging in via "Login to account" and choose menu item "SIP/IAX Info". In the middle of the screen you will see:
SIP URI : freesip.net
Username : for_field_User
Пароль : for_field__Password
Fill in this information to fields User and Password of web-phone and click Login. Once you see Registered! and web-phone keyboard - you are ready to call!