The REST interface is bundled with eZ Publish 4.5.0. If you wish to use it, you need to make the the REST endpoint, index_rest.php available via rewrite rules. Conversely if you prefer not expose this functionality, you need to make sure that the this file is not exposed in your rewrite rules, either via .htaccess files, or virtualhost configuration.
Click this link to find the rewrite rules.
Now you can continue the tutorial here: