Asus RT-N66W - Manual (Page 52)

4.1.2 WPS
WPS (Wi-Fi Protected Setup) is a wireless security standard that
allows you to easily connect devices to a wireless network. You
can configure the WPS function via the PIN code or WPS button.
NOTE: Ensure that the devices support WPS.
To enable WPS on your wireless network:
1. From the navigation panel, go to Advanced Settings >
Wireless > WPS tab.
2. In the Enable WPS field, move the slider to ON.
3. WPS uses 2.4GHz by default. If you want to change the
frequency to 5GHz, turn OFF the WPS function, click Switch
Frequency in the Current Frequency field, and turn WPS ON
again.