You still need to configure your Bit.ly plugin to make it work!
To work, the plugin needs a bit.ly username and API key. You can find your API key on your Bit.ly Settings page. Then add the following to your site’s wp-config.php, anywhere before the “stop editing here” line. Don’t forget to replace “<your username>” and “<your API key>” with respectively your username and API key:
/** * Settings for Bit.ly Shortlinks Plugin * https://yoast.com/wordpress/bitly-shortlinks/ **/ define('BITLY_USERNAME', '<your username>'); define('BITLY_APIKEY', '<your API key>'); // optional, if you want to use j.mp instead of bit.ly URL's define('BITLY_JMP', true);