by default once the wlan ssid is enabled, it will be broadcasted by all the operational ap's. wlan override feature lets you choose which ssid's to broadcast and/or suppress.

to know what SSID an ap is broadcasting. in the gui, simply goto wireless>all ap's>click on the ap name> scroll down at the bottom of the page. if wlan overdrive isn't configured, all enabled SSID's are broadcasted. Otherwise, you will see a list of SSID's on the WLAN override option.