I have my Plex Server on my Shield TV and am not able to add photos on my desktop hard drive to the library on my server. Plex doesn’t see my desktop hard drive. How can I correct this?
If you want to keep the photos on your desktop only, You need to enable sharing of that HD/folder on your desktop, then in the Shield settings connect to that. ( your desktop needs to remain on at all times so it has access to them.)
https://support.plex.tv/articles/220391808-media-storage-options-for-nvidia-shield/#toc-2
If you mean you want to copy the files to your shield you need to enable sharing on the shield so your desktop can see it.
https://support.plex.tv/articles/220347688-accessing-shield-storage/#toc-0