Connect the router to your PC with a serial cable and use the following Hyperterminal settings:
Connect using: COM1
Bits per second: 9600
Data Bits: 8
Parity: None
Stop bits: 1
Flow control: none

press enter in Hyperterminal to get connectivity to the router.
Type “en” at the “router>” prompt or type in a username/password if the router is requesting it.
router>en
router# conf t
router(config)# int f0/0 (or another interface you want to configure)
router(config-if)# ip address <ip address> <subnet mask> (ex. 192.168.1.1 255.255.255.0)
router(config-if)# no shut
router(config-if)#exit

now configure the next interface:
router(config)# int f0/1 (or another interface you want to configure)
router(config-if)# ip address <ip address> <subnet mask> (ex. 192.168.2.1 255.255.255.0)
router(config-if)# no shut
router(config-if)#exit

no configure the default route to point to the next hop for the F0/1 interface
router(config)# ip route 0.0.0.0 0.0.0.0 <next hop IP address> (ex. 192.168.2.2)
router(config)#exit
router# write memory (to save your changes)

now plug in a crossover cable to the F0/0 interface and you’ll be able to connect to devices past the F0/1 interface.