Originally Posted by Cellus

There are two standard methods of accessing the user interface for a Cisco router - direct console connection via serial cable, or via telnet. There is no "web interface" so to speak.

Cisco routers are complex, the interface is pure command-line and somewhat esoteric, and doing anything without knowing what you are doing can wreck things badly. I highly recommend you pick up a manual before you even dare tinkering around with anything. Any book relating to Cisco routers and IOS should be fine - the IOS interface is pretty much universal for all of their routers, so you do not need a book for a specific make or model.

Addendum: Cisco routers are not like your Linksys/D-Link/Netgear baby Home/SOHO routers. Cisco routers are enterprise-grade routers, and approaching them with the same nonchalance as your home router would be a bad idea.