@JohnEsben 

Hi, thanks for posting question here.

To access the web management interface of your Router, you may simply connect a PC to the Router network (either through Ethernet or Wi-Fi), open a browser, in the browser address bar, put in http://tplinkmodem.net or http://192.168.1.1 (192.168.1.1 is the default LAN IP address of the Router).

For more information, please refer to this guide.

If you are having trouble opening/accessing/reaching the web management interface, here are some tips for you:

    1) Please make sure your PC is connected to the main network of the Router, not a guest network or other networks, or simply using a wired connection to the Router.

    2) Use "Incognito mode" or "Private mode" in your browser.

    3) Try other PCs or phones.

    4) Disable the "Access Control" feature on the Router.

Or you may refer to the troubleshooting guide.