Make sure Composer is installed globally, as explained in the installation chapter of the Composer documentation.

Open a command console, enter your project directory and execute:

$ composer require projet-normandie/twitch-bundle

Then, enable the bundle by adding it to the list of registered bundles in the config/bundles.php file of your project:

// config/bundles.php

return [
    // ...
    ProjetNormandie\TwitchBundle\ProjetNormandieTwitchBundle::class => ['all' => true],
];

# config/packages/projet_normandie_twitch.yaml

projet_normandie_twitch:
  client_id: '%env(string:PN_TWITCH_CLIENT_ID)%'
  client_secret: '%env(string:PN_TWITCH_CLIENT_SECRET)%'