D-Link DIR-850L User Manual page 22

Section 3 - Configuration
If the router detected or you selected Static, enter the IP and DNS
settings supplied by your ISP. Click Next to continue.
For both the 2.4GHz and 5GHz segments, create a wireless network
name (SSID) using up to 32 characters.
Create a wireless security passphrase or key (between 8-63 characters).
Your wireless clients will need to have this passphrase or key entered
to be able to connect to your wireless network.
Click Next to continue.
In order to secure your router, please enter a new password. Check
the Enable Graphical Authentication box to enable CAPTCHA
authentication for added security. Click Next to continue.
D-Link DIR-850L User Manual 17