I think that if you need a .htaccess file, then you should really be looking at tutorials for that. This is explaining about Silex and therefore shouldn’t need any explanation about NGINX or Apache settings.
This is a pretty good tutorial and I feel that it doesn’t need any explanation of where you should point your server’s config files or place your htaccess as everyone does work differently.
If you were to look at any documentation for Laravel, Symfony, Silex etc, you will not find anything which goes into detail about how you do this as it is completely up to the user.