D-Link DIR-868L User Manual page 41

Section 4 - Security
If you selected Automatically, the option to make your password the same
on both bands with be ofered. If you choose to make them the same, you
can select your own 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-868L User Manual 37