|First, read the manual/setup guide. It will tell you what IP to connect to.|
If that doesn't work, then you should reset the router to factory defaults (as per the manual) and try again. If you still can't get into the management interface on the router, take it back to wherever you bought it, explain the situation and they'll either replace it, or figure out what's wrong and make it work.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.