In order to get into a Cisco router, you will need a Cisco Rollover cable to connect to an available Serial port on your PC. The other end of the cable goes into the Cisco Router's CONSOLE port.
In order to reach the router via IP address, you will have to do so through an interface OTHER than the CONSOLE port. You will also have to configure the router to connect via telnet.
(in config mode, use the following command):
line vty 0-4
login
password password
(the 2nd password is the actuall password... the first one must be 'password' as shown... to make the password Cisco, it would be:
password Cisco