Enter your details / credentials in config.php

it should look something like

<?php

return [
    'client_id' => 'xxxxxx',
    'client_secret' => 'yyyyyyy',
    'account_id' => 'zzzzzzz',
    'webhook_app_secret_token'=>'123123123',
    'oauth_client_id'=>'xxxxxxxx',
    'oauth_client_secret'=>'yyyyyy'
];

?>

If you don't already have php curl installed sudo apt-get install php-curl

If you dont already have firebase php installed composer require firebase/php-jwt