To access the web configuration interface use your browser with the following URL:
http://<ip_address_of_your_device>:8080/
If you don't know the device IP address you can use the Microsoft "Windows 10 IoT Core Dashboard" application to find the device and give you its IP address.
Log in:
Username: Administrator
Password: your password
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.