Mac book 3,1 / Mac OS X 10.6.8

You don't need the software from Western Digital. Use Disk Utility to format the drive as HFS extended journaled not case sensitive.

The online documentation tends to be constantly updated with newer system versions in mind and unfortunately old versions are not kept, particularly one that has not been used in the past decade. For example, this is the link that used to be tell you how to use Disk Utility but I can tell it would be very difficult see how it relates to your situation:

How to erase your Intel-based Mac - Apple Support

I run an old system but definitely not as old as yours so I don't know how much my telling you with reference to the one I am using may lead to confusion. (By the way I am also busy doing a ton of other things at home and my doing this would require my sitting here for a long time -- don't forget the people responding here are users like you, volunteers and not Apple employees.)

Go to your Applications folder > Utilities and open Disk Utility. Once it is open, on hte left you will see a list of your drives. Find the Western Digital one and highlight it. You may discover there is a top level drive and then an indented other drive below that which is hte one you want to select. The top level one is the physical drive itself and the indented one is what is known as a partition on the drive which is what appears on your Desktop. A series of tabs should be along the top of your window and one will say Erase. Select the options I described earlier and erase the drive.