How to connect Yandex.Checkout?

Question

Composer

I connect according to the instructions Yandex.Cashier in the project on Laravel
What does it mean:

Include dependencies
require __DIR__ . '/vendor/autoload.php';

Where to connect them?
And did I understand correctly that I should do the next step (import the cash register classes, create classes and call the method) in the handler method after clicking on the "Pay" button?

Answer 1

https://laravel.com/docs/5.6#installing-laravel
Or do you use laver without composer?