What's the simplest way to back up my TNAS (or at least certain folders / drives on my TNAS) onto another device? Specifically, I want to backup certain folders from my F5-221 to my now spare WD MyCloud Home.

Basically the MyCloud device is spare and I was going to use it as a spare backup of photo's and family videos etc. Rsync has been suggested but not quite sure how to get that working with the MyCloud?