D-Link DSL-3590L User Manual page 133

Section 5 - Connecting to a Wireless Network
3. Enter the same security key or passphrase (Wi-Fi password) that is on
your router and click Connect.
It may take 20-30 seconds to connect to the wireless network. If the
connection fails, please verify that the security settings are correct. The
key or passphrase must be exactly the same as the one on the wireless
router.
D-Link DSL-3590L User Manual 129