1. The file "config.php" will actually be named "config_adoptables.php"; you need to rename it to config.php.
2. You will not be able to carry out the instructions they have there, since you are not allowed to access files that have 777 permissions via the web server (you'll get a 403 Forbidden error if the files have greater than 644 permissions), so you'll probably need to edit the config.php file manually.
Since you have apparently been to the Mysidia Adoptables forum already, and they are the people who actually know what you need to know, why not ask there?