Im assuming your laptop doesnt have a serial port,
so what you can use is a Serial->USB Cable and a terminal emulator such as Putty,
here are the links:
Serial -> USB
If the laptop is older, and has a 9 pin serial port, we would use the blue rollover cable, with the DB9 connector attached to the PC serial interface, and the RJ45 connector plugged into the console port on the router.
If the laptop doesn't have a 9 pin serial port, we would use a USB to 9 PIN adapter, then use the blue cable as well.
Routers ship with a blue console cable, but they can be purchased separately as well, along with the USB to serial adapter.
Here is one that includes both pieces: