How to correctly connect the PHP library of the Yandex.Market partner API via composer?

Question

Composer

All the best.

I'm just starting to work with composer, help me figure it out.
There is a Yandex.Market partner API library on github - https://github.com/yandex-market/marketplace-php-p...

I do everything according to the instructions, as it is written:

through the terminal, the composer require yandex-market/marketplace-php command -partner
As a result, it creates a vendor folder and composer.json with the following content:

{
"require": {
"yandex-market/marketplace-php-partner": "^3.2"
}
}

Then, in the index.php file, at the very beginning I connect autoload:
require '../vendor/autoload.php';

As a result, when trying to use the class, it says that the class was not found.

What am I doing wrong?