In order to access the newsgroup, you need to set your news server (sometimes called the NNTP server) to news.rice.edu.
To do this, hunt around the various Preference menus, or Internet Settings programs, on your computer. If that doesn't work, ask a computing consultant in Mudd or at your college, or ask for help during lab.
Note Owlnet policy is to not allow newsgroup-access from off-campus (well, from outside the rice.edu domain).