You could try these:
Or read some of the FAQs. They used to be pinned on the forum, but someone at WD must have decided they were no longer needed…
A NAS is simply a network-connected disk (well, it’s not quite that simple…). But, if you map it into your computer’s file system, it can be accessed by any program running on your computer, just as if it was an internal or USB HDD. Then you can use your familiar file manager to move files about, or use a backup tool. You do not have to use WD tools to access it; pick a backup tool you like.
As for syncing. mirroring, backup and file transfer, a little googling will find good tutorials on the subject. It’s worth understanding the different options. It doesn’t help that WD picked their own terminology, rather than using standard computer jargon (e.g. ‘Share’ for folder, or directory).
