Where is my Router Configuration Page?

Hey, I have an Orange Siemens Router, and i want to change some settings (frequency, ports, channels etc.) and I read you have to visit a "Router Configuration Page"- is this some kind of website you visit? anyway i've seen some links for Netgear etc. but none for my router, to be honest, im just looking for a link to the Orange/Siemens Configuration Page, if you give me a decent answer you are a hero :D