To change the password you would use the Install CD 1. The second one is used only during a complete install of the system which you aren't going to do.
The Restore CDs would be used in numerical order if you were going to reinstall all of the software that came on the machine when you bought it. The DVD actually has all the software on one disc because it can hold much more than a CD. Since you have the DVD disc you must have the CD/DVD burner model.
The Hardware test CD is used if you are having problems and suspect something may be wrong with the machine itself, not the system running on it. It has software that can test the eMac to see if there are problems.
The install CD with the iMovie, iTunes, etc. is just in case you have to reinstall those particular applications.
The World Book is an encyclopedia. It may already be installed on the hard drive and that is just a copy for possible reinstallation. Look under Applications on the hard drive and see if you find a World Book folder. If so, just put the disc and all the other CDs in a very safe place. The World Book program may ask you to insert the CD in the drive when you activate the program.
If the World Book is not installed you can just insert it in the CD player and when the icon pops up on the desktop, double click and it will probably ask to install a "player" and some info on the hard drive. That's fine. However it may ask for your administrator's password before installing. Maybe not, depends on what and where it wants to put things. Then you can run the encyclopedia program any time you want. If I remember correctly it asks whether you want to install the full program or just the bare bones. The bare bones means you would have to put the CD in the drive whenever you wanted to run it so it has access to the videos on the CD. An alternative way is to copy the whole CD to the drive but it will take up probably 600MB of space. If you access the encyclopedia a lot and have a large hard drive with little on it this might make sense. Otherwise just put it in when you want to use it.
The disc labeled Verbatim is most likely a blank CD or DVD for your use in burning on the eMac. I know at least one blank comes with that machine. Verbatim is a brand name of a manufacturer of storage items.
I'm heading up to my folks' house tomorrow and they have an eMac so I can play with their machine if you have any further questions.
Basically all you need do now is either find your administrator's password or reset one by using the Install CD 1. Then you can put the discs away and hope you never have to touch them again. (except the World Book and the blank)