This article describes how to enable wireless security.
INSTRUCTIONS & INFO
From a device that is connected to the AT&T Wireless Internet network, open the web browser then go to http://att.wirelessinternet. Enter the Admin Login, then click Login. Note: The default admin login is attadmin. The admin login can be found on the bottom of the device.
Edit the security settings as desired. Note: Security settings will apply to all connected devices. If you change these settings, existing connected devices may lose their connection and have to reconnect. The AT&T Wireless Internet provides both 2.4GHz and 5GHz networks, which can be controlled separately.