What specific My Cloud device do you have? One can see a graphical depiction of My Cloud devices (not My Cloud Home as that is a completely different device) at the following link:
If you have a single bay My Cloud have you checked that SMB1.0 is enabled in Windows? Microsoft disables the SMB1.0 option in recent update(s) to Windows 10.
While one can use WD Sync software (which can be downloaded from the WD Support site) to sync user files from their computer to the My Cloud. More than a few have had trouble with the software. Some have turned to using third party sync software like the Free File Sync (https://freefilesync.org/) for local network syncing/mirroring with the My Cloud.
For backing up a computer one can use Apple’s Time Machine if using a Mac, or Smartware if using Windows. Smartware can likewise be downloaded from the WD Support site. Or one can use a third party backup program (there are a number of free and paid programs) to backup a computer to the My Cloud on the local network.
It also helps to read the My Cloud User Manual, which can be obtained from the WD Support site, as the User Manual generally details how to use the various features of the My Cloud device including how to “map” Shares.
A WD Support article that covers when Windows or Mac cannot find the My Cloud.