When using NFS, articles posted on a local host have to be forwarded to the central machine, because accessing administrative files might otherwise expose the system to race-conditions that leave the files inconsistent. Also, you might want to protect your news spool area by exporting it read-only, which requires forwarding to the central machine, too.
C-News handles this transparently. When you post an article, your newsreader usually invokes inews to inject the article into the news system. This command runs a number of checks on the article, completes the header, and checks the file server in /usr/lib/news. If this file exists and contains a hostname different from the local host's name, inews is invoked on that server host via rsh. Since the inews script uses a number of binary commands and support files from C-News, you have to either have C-News installed locally, or mount the news software from the server.
For the rsh invocation to work properly, each user must have an equivalent account on the server system, i.e. one to which she can log in without being asked for a password.
Make sure that the hostname given in server literally matches the output of the hostname(1) command on the server machine, else C-News will loop forever when trying to deliver the article.