Do you mean actually sync or just backup one My Cloud to another in a remote location? Sync and backup are two different tasks.
The subject of syncing one My Cloud to another in a remote location has been discussed in quite a few prior threads, see some of those threads below. Do a forum search (magnifying glass icon upper right) for various threads discussing backing up one My Cloud to another in a remote location.
http://community.wd.com/t/how-to-sync-two-mycloud-at-different-locations/145528
http://community.wd.com/t/setting-up-offsite-mirror-drive-for-mycloud/151187
http://community.wd.com/t/how-to-sync-myclouds-at-different-locations/150933
http://community.wd.com/t/how-to-sync-2-wd-my-cloud-4tb-drives-on-two-remote-networks/162261
http://community.wd.com/t/sync-between-two-my-cloud-2tb-off-site-backup-my-cloud-to-my-cloud/170353
http://community.wd.com/t/sync-back-up-3-different-locations/164417
