i'm going to assume you have a cable/dsl connection already. since you didn't specify the Brand name of your router, I'll go with the basics...
From your broadband (cable/dsl) modem, take the CAT5 network cable (thats the one that looks like a phone jack) and plug it into the WAN port on your router (the WAN port is usually separated away from the LAN ports on the back). If the wireless card on your iBook is set to "automatic", you should be pretty much good to go...If it isn't then try some of these steps..
First, you'll need a 2nd network cable to plug from one of the LAN ports on the router to your iBook....then type in these numbers in your web browser's address bar...
192.168.1.1 (for Linksys) OR
192.168.0.1 (for D-Link) OR
check the router manual for the DEFAULT router address....
This will get you to the routers configuration utility page...
after that, there should be a tab you can click for DHCP...insde that area, there should be a DHCP CLIENTS list...click that and see if your computer is listed TWICE there (one will be your wired connection, the other is the wireless)...The address should read...
192.168.1.1xx (say 100 for the wired)
192.168.1.1xx (say 101 for the wireless)
(these are linksys router addresses...substitute 192.168.0.1xx for D-Link, or whatever your router address is)
If you DON'T have 2 numbers listed in the client list, you will have to go in and set your wireless card up manually...
get to the wireless card's properties, find the TCP/IP protocol list, and set it up to look like this....
IP address: 192.168.1.100
Sub-Net Mask:: 255.255.255.0
Default Gateway: 192.168.1.1
(again, these are linksys addresses, make the usual substitutions for other brand names, but keep the sub-net mask numbers).
Note here that these techniques used for Windows-type systems, but as far as manually configuring your wireless card, these steps should work for you....
good luck