Editing Files Owned by Root in /etc

I use a terminal window to ssh to a remote server. The connection gets terminated after a short period of inactivity. I searched and found that I can solve this problem by editing a configuration file in /etc. But when I try to do that using emacs, it opens in "read-only" mode--the file is owned by the root account. How can I edit this file? Thanks for any help you can provide.