Question Composer Help

[softvet]

Hy
Is the first time when I work with plesk composer
I have to install a new pachage postmark-php
I download all file from GitHub - wildbit/postmark-php: The official PHP library for Postmark. and I put this folder in /include/postmark-php-master
So , the file composer.json is in include/postmark-php-master/
but php composer not see this folder
what can I do?
Thanks