1. Go to this page and download the library: Download 2lenet/entity-file-bundle 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/ */
$entityFile = $manager->save($seller, $data, "unicorn.png");
$entityFile->setDescription("Picture of a very sexy unicorn");
$this->em->persist($entityFile);
$this->em->flush();