If you have access to the database: reset the Piwigo webmaster account's password to gain an initial login. See [Forum, post 181215 by erAck in topic 31381] Lost password.
If you don't have access to the database because you don't know the credentials: they are in your Piwigo's local/config/database.inc.php file.
If you don't even have access to that or if this is all gibberish to you and you are the domain owner with Godaddy then ask them to do it and find someone who'll maintain your site.