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 tplinkwifi.net and to access to below login page. Type the Username and Password, then click "Login".
The default login of the router is available on the sticker at the back of the router. If you have done a configuration on your router previously, the password may be different)
For example, below is the login details of the above router:
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, choose Basic and then click Wireless tab on the left menu to access to below screen.
6. Since this is a dual band router, you will have 2 Wireless Network 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 Wireless Network Name (SSID) and the Password to follow your preferences, then click "Save" for the changes to take place.
Please reconnect to the new wireless name with the new password once completed.