To create a listener you need to something similar in your class:
use Bolt\Events\CronEvents;
$this->app['dispatcher']->addListener(CronEvents::CRON_INTERVAL, [$this, 'myJobCallbackMethod']);
CRON_INTERVAL should be replace with one of the following:
* CRON_HOURLY
* CRON_DAILY
* CRON_WEEKLY
* CRON_MONTHLY
* CRON_YEARLY