Ssid for different network

running openwrt in an Alix 2d13 with a mini pci card Gigabyte for wifi. Wifi gets dhcp in the same IP range as my LAN( i would like to add a second SSID for another subnet( that will have access to the Internet. the 2 subnets they should not be able to talk to each other. Could someone help me to configure that in LUCI please?

This is similar to what you need to do, adapt it to your needs