This option only makes sense for Public communities. How admin can manage the messages section?
In Admin Panel> Portal Settings> Messages you can define Welcome Message, Signup rules, Question intro, User intro, Topic intro, and User Terms and Conditions.

- Welcome message is the message that will be displayed on top of your home page, if a user is not logged in. In the picture below, you see the Welcome message defined as "Join the community of community managers":

- Signup rules message will be displayed under the Sign Up box:

- Question intro, User intro, and Topic intro are the messages that will be displayed when a person is not logged in, and he/she clicks on a question, or a topic, or a user profile. It reminds the external visitors to log in/sign up to access your community.



- User Terms and Conditions is a message that appears on the sign-up page. By adding a message to this section, a check box will be added to the sign-up page and by clicking on the check box, your members are agreed to your Terms and Conditions (T&Cs). You can put a message like "By clicking on the check box, you are agreed to our T&Cs). You can attach a link of your T&Cs page to the message as well, so users can click on it and read it before clicking on the check box.
