Hello @manish !

First of all, you need to have a common module's skeleton described here:

https://github.com/unacms/una-vendor-test/wiki

The 3rd party package can be placed in the plugins folder and connected to the main Module class in this way like in the old variant of OAuth2 integration:

require_once (BX_DIRECTORY_PATH_PLUGINS . 'OAuth2/Autoloader.php');
OAuth2\Autoloader::register();
class BxOAuthUserCredentialsStorage extends OAuth2\Storage\Pdo implements OAuth2\Storage\UserCredentialsInterface