WDMYCloud EX2 Win Server Internal BCK Network

My Cloud OS 3 Personal & Network Attached Storage My Cloud EX2
1

Hello,
I have a Win Server 2012 r2 that has been having trouble detecting an older WD Book via usb.
So I purchased the WD Ultra EX2 in hopes of backing up the server via network internally to the drives in the WDEX2.
I tried getting the device to Join the domain with no success. Im wondering when do I need to add the device to AD First like you would any normal computer? Although Ad will normally pick up the computer and add in some cases? I have turned on SMB 3
I believe my issue is with the device not joining the domain.
If all else fails I will connect it via usb last resort.
How do I get the WD Device to see the the data on the server? I would like to just simply map the data on the server to the device and run some basic backups.
SMB ? Any help or point me the right way would be great! Stay safe…