Some routers use 192.168.0.1 as the default. Some routers allow the user to change the default IP address. Many have the default IP printed on a label along with the default userid and password on the bottom or back of the router. Also refer to the user manual. Connect the PC to the router via a good Ethernet cable. For many TP Link routers, you can use http://www.tplinklogin.net/. If your router does not connect using the default, clear your browser history, power cycle the router and PC, and try again, try a different browser, try a different PC, and if none of those work, reset to factory and then reenter your settings.