1. Go to this page and download the library: Download jitsu/app library. Choose the download type require.
2. Extract the ZIP file and open the index.php.
3. Add this code to the index.php.
<?php
require_once('vendor/autoload.php');
/* Start to develop here. Best regards https://php-download.com/ */
(new MyApplication())->respond(
new \Jitsu\Http\CurrentRequest(),
new \Jitsu\Http\CurrentResponse(),
new \Jitsu\App\SiteConfig(__DIR__ . '/config.php'));