To set up archiving the logs, set th DB config parameter LOGARCHMETH1. See the online help or the manuals on how to set this. As for deleting them, DB2 provides no method to do this. You have to do it either manually or through some cron type process. Just make sure that you only delete archived logs that are no longer needed. This means that you have to be 100% sure that should a failure occur, and you have to restore the DB from the backup image, that these logs are not needed for rollforward recovery.
HTH
Andy