D-Link DIR-865L User Manual page 41

Section 4 - Security
If you selected Manually, the option to make your password the same on
both bands with be offered.
Enter your wireless password in the box below.
Click Next.
You will now see a summary window that displays your settings. Write down
the security key and enter this on your wireless clients.
Click Save to save your settings.
D-Link DIR-865L User Manual 37