How can I use my WD My Cloud drive, which is attached to my router, in conjunction with Plex?

A network technician came to help my family out today and suggested we get Plex and use it from our WD My Cloud device. I cannot find any instructions on how to do that. Any suggestions? Thanks!

you need to mount the drive on your computer with the server so the server can see it. WD should be able to give you instructions on how to mount a drive but here is some basic info on how to do that