How to access your time warner router?

Because I type in the default gateway I get nothing but page not found I try the release thing and renew I get nothing at all, and the time warner guy said that are multiple port thing would not work, we barley got this computer to connect to the internet and my brothers, and it won't work with the port thing, unless its running to this computer and at that time it won't even run for my brothers, and my xbox 360's won't even connect to the internet does anyone know how to fix this and give me your emails if you don't care so I can ask further questions