Add genkgo/api to your dependencies and install them. You can have a look at one of the examples or see the docs.
<?php
require_once '../vendor/autoload.php';
use Genkgo\Api\Connection;
use GuzzleHttp\Client;
$config = require_once 'config.php';
$connection = new Connection(new Client(), $config['url'], $config['token']);
$folder = $connection->command('organization', 'find', [
'name' => 'Aanmeldingen'
]);