Are you hoping to completely disable wireless connectivity or just wireless administration? Here is a link to the router manual. It discusses the former in a few easy steps... the latter may be more difficult.
Log Into Router
Select Wireless Settings under Advanced in the main menu.
The available settings in this screen are:
• Enable Wireless Router Radio. If you disable the wireless router radio, wireless devices
cannot connect to the WNR1000v2 router. If you will not be using your wireless network
for a period of time, you can clear this check box and disable all wireless connectivity.
• Enable SSID Broadcast. Clear this check box to disable broadcast of the SSID, so that
only devices that know the correct SSID can connect. Disabling SSID broadcast nullifies
the wireless network discovery feature of some products such as Windows XP.