@BarjargBabe,

Most of our devices will be tied to your TP-Link ID, first, try to log into the web interface using your TP-Link ID and Password. Otherwise, there should be an option on the login page for if you "Forgot Password?" The Login Page can be found by navigating on your home network to: http://tplinkrepeater.net.

Otherwise, you can connect to and set up the range extender using the Tether App on your Phone. The Tether App will also use your TP-Link ID and should be the same credentials that you should use to access the router through the web interface, but will provide a much more user-friendly and intuitive interface