You may proceed with the following troubleshooting steps and it shouldn’t take you much longer  than 15 minutes.        

1. Please standby a computer/laptop to access to the internet and connection must be via LAN cable (connect the LAN cable to the Black port at D-Link Router and direct to the computer/laptop).

2. You may open any web browser such as Google Chrome, Internet Explorer, Mozilla Firefox and etc.    

3. On the address bar, please go to http://dlinkrouter.local./ and below page will appear. (These are the defaults and if you have done a configuration on your router previously, the password may be different).          

Username: admin          

Password: (Leave the field blank)

4. Once you have successfully login, the router's web-based setup page will appear. Please follow below steps for the configuration.

5. From the top menu, click Settings and then choose Wireless.

6. Below screen will appear to configure the wireless setting. Since this is a dual band router, you will have 2 Wi-Fi Names (SSID) i.e. 2.4GHz and 5GHz.

You may connect to any of the SSID, preferably with a stronger signal available.

7. You may change the Wi-Fi Name (SSID) and the Password to follow your preferences, and then click "Save" for the changes to take  place.

Please reconnect to the new wireless name with the new password once completed.