Each time a user logs in to a system, the message of the day in the file /etc/motd is displayed. Use /etc/motd to give users information specific to the system, which someone logging in would want to know. Make sure /etc/motd has read permission to others and write permission to root user only:
1) Login as root or become root user using su
2) Use text editor vi to edit /etc/motd
# vi /etc/motd
3) Edit and save the changes. Next time the user logs in she will be able to see changes.