D-Link Wireless AC1200 User Manual page 20

Section 3 - Configuration
In order to secure your DIR-850L, enter a new Admin Password. You will
be prompted for this password every time you want to use the router's
web configuration utility.
Click Next to continue.
The Summary window will display your settings. Click Back if you find it
necessary to make changes. When the settings are correct, make a note
of the of them so you can configure your Wi-Fi devices.
Click Next to continue.
D-Link DIR-850L User Manual 15