By default, wifi was not enabled by the firmware. Use the following command to enable
ssh -l root 192.168.1.1
inside router
opkg update
opkg install hostapd wpa-supplicant kmod-ath9k
Now you can go to the luci menu > Essentials > Network > wifi to enable and provide password
To enable DDNS
opkg luci-app-ddns
configure it luci menu > Essentials > Dynamic DNS