You have a network storage device that you have files on that you'd like to mount under OS X?
Is the NAS a Unix/Linux back end? Basically, are the shares SMB/CIFS? Or NFS? Or what?
If you have the name or IP address, you can try:
Finder > Go > Connect to Server > smb://NASname/sharename
Or nfs://NASname/sharename
You'll need to have login credentials to access those files, and it will ask for them, and then let you save it in the keychain.
Hope that helps.