How do I use a local network NAS for storage?

Description: Windows 7 Dell Optiplex 3020 PC with new PLEX server install (1.0.3.2461-35). Program is OK and running, but can’t see media folder on my local network NAS. Nothing on the net has an issues using the NAS. Only the PLEX setup program does not see it. I did try mapping the folder to the PC but on joy.
A forum search found lots of NAS install warnings and information but I was unable to locate any help for a PC installed server using a NAS for its media storage. I know this has to be easy, but I’m out of ideas and the grand kids are getting worried.

You need to map a drive from your NAS drive to your Windows machine.
For example, make a folder on your NAS called Movies and share that. Then map Windows to that share on Drive letter Z in Windows and tell Windows to reconnect on logon.
Then tell Plex to use that Drive (Z:) in your Movies library. Plex will sccan the folder on it’s scheduled scan or you can force a scan.
Do the same if you are going to use it for TV Shows also.Create a folder called TV Shows, and share it, then map a drive in Windows to that share. Tell Plex to use that drive in your TV Shows library.
I am assuming you know how to create folders on your NAS and share them. I am also assuming you know how to map a drive in Windows.

Are you able to see the mapped network drive folders from the NAS on the windows 7 PC - using the same account that Plex Media Server runs in?
Are you able also to access the share on the nas through \\NAS-Device-Name\Share-Name on the PC ?

Are you running Plex Media Server as a service or using standard functionality ie as a process started on boot up/login to the windows account?

There are some issues with Mapped Network Drives and UAC - see this article
technet.microsoft.com/en-us/library/ee844140(v=ws.10).aspx

Can you browse to your NAS from Windows and see your Movie/TV folder even when its not mounted?

What happens when you tried to map your Movie/TV network share (located on the NAS) to your PC? What error messages, do you need a username/password?

Mounting shares on Windows
Mounting shares on Windows systems is generally handled by using ‘Map Network Drive’ in Windows Explorer or UNC paths.

Map Network Drive
To Map a Network Drive:
Open Windows Explorer
Mount the Share
Right-click the Share and choose Map Network Drive
Choose a Drive Letter
Note: Be sure to choose a Drive letter like Z:. If you choose a Drive letter close to your regular drives, the drive letter mapping can be changed by adding a new drive to your system.

I am so impressed! Three helpful responses in 15 under minutes and no one called me stupid. The good news is I’m all setup in PLEX and just served my first movie. WOW!
It turned out I was really close. The mapping worked fine but the server did not see it till I restarted it after dinner. I mapped the Music and Photo folders, restarted PLEX again and had all three.
So the bottom line (I hate it when people say that) is problem solved in less than 15 minutes. All the advice was on target and very helpful. This forum really works.
Thanks again guys.