The most recent versions of Composer add the bundle to the configuration for you, but in case an earlier version of Symfony is used the bundle can get added to the list of bundles in your AppKernel class as shown below:
composer require apy/breadcrumbtrail-bundle
<?php
// app/AppKernel.php
public function registerBundles()
{
$bundles = [
// ...
new APY\BreadcrumbTrailBundle\APYBreadcrumbTrailBundle(),
];
}