1. Go to this page and download the library: Download backpack/language-switcher 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/ */
@ 'flags' => true, // true by default, change it to hide flags
'main_label' => false, // false by default, it may also be a string, for instance "Language"
])