D-Link DIR-451 User Manual page 51

Section 5 - Connecting to a Wireless Network
3. The Wireless Network Connection box will appear. Enter the
WPA-PSK passphrase and click Connect.
It may take 20-30 seconds to connect to the wireless network. If the
connection fails, please verify that the WPA-PSK settings are correct.
The WPA-PSK passphrase must be exactly the same as on the
wireless router.
D-Link DIR-451 User Manual 51