How do you set the ibook g4 background?

Screen savers are set up in the DeskTop and Screen saver section of the System Preferences. After selecting which screen saver you wan to use you can either set a time delay so the screen saver starts after the computer has not been used for a few minutes or set a Hot Corner which will activate the screen saver when you move your mouse to the set corner.

To install new screen savers you can usually double click on the saver file and it will be installed for you.