D-Link DIR-866L User Manual page 44

Section 3 - Configuration
If you selected Automatically, the summary window will display
your settings. Write down the security key and enter this on your
wireless clients. Click Next to continue.
If you selected Manually, the following screen will appear.
Check the box if you want to use the same password for both
the 2.4GHz and 5GHz bands. Create a passphrase for your
security password. Click Next to continue. You will see the Setup
Complete screen like the one above.
Note: The security password/passphrase must be between 8 and
63 characters and is case-sensitive. You will need to enter this
passphrase on your wireless clients exactly or it will not connect.
D-Link DIR-866L User Manual 39