D-Link AC750 User Manual page 192

Section 5 - Connect a Wireless Client
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-818LW User Manual 187