Problem A FortiGate unit provides your office with wired networking, but employees also use laptops and mobile devices. These devices need secure WiFi access to both the office network and the Internet. The employees use web applications and are most comfortable authenticating through the web browser. Solution Set up a FortiGate WiFi captive portal configuration that intercepts connections to the wireless network and displays a portal on wireless clients’ devices. User’s must authenticate with the portal to get access to the wireless network. To configure the portal you must create a user group on the FortiGate unit with a user account for each employee. Create a FortiGate WiFi network with captive portal authentication. A captive portal appears to be an open WiFi access point, allowing any WiFi device to connect. On the first attempt to connect to a web site, the captive portal presents a web page that requests the user’s login credentials which must match credentials in the user group.
The original article/video can be found at FortiGate Cookbook – Secure WiFi with a Captive Portal