There are only 2 settings here that regular users will access. That is the Reply-to Admin email address and the Reply-to Security email address. These addresses are necessary if you are sending emails to your users. For example, you must fill in the Reply-to Admin address to send password resets, new user registration confirmation, etc. The Reply-to Security email address is used for Incident clients only.
To get to the Classic Settings page, click on System Config then click on Classic System Settings
The Edit System Config page displays. This will allow you to update the system with the latest information (mail address, phone numbers, etc). When you are done editing, click Update Record and Refresh the page. Your changes will now be reflected.