everyone here is close, and you might stumble on the right answer, but what you really want to do is point your web browser to your internet gateway (at least generally and assuming a typical setup). if you use the ipconfig command line utility you will probably see that your IP address is something like 192.168.1.x and your gateway would be 192.168.1.1 or 192.168.1.254. It will probably prompt for a password at this point which is typically something like just typing admin in the password section or admin/admin or admin/password something along those lines. For example:
Linksys routers are typically at 192.168.1.1 with admin in the password (some require a username of admin too).
Netgear routers are typically at 192.168.0.1 with admin and password.
Belkin routers typically don't have a password and are at 192.168.1.1
D-Link routers are 192.168.0.1 with username admin, password is left blank.
AT&T DSL or Uverse routers are typically 192.168.1.254 and the password is on the side or bottom of the unit (it's the serial number).
Comcast modems are normally 10.1.10.1 and the password is normally set by the technician who delivers it.
Finally Apple Airport Extreme units have a special app you need.