To use the form all you need to do is to enter the address of both the original image to be displayed on your page and the one you want it replaced by when the mouse is moved over it. You also need to enter the width and height of th images (which sould be the same for both) and alternate text to be displayed by those viewing the page with images turned off.
The next step is to copy the HTML for the various Image Tags and paste them as code into the body section of your web page where you want each image to appear. Unless you want all of the images to appear next to one another this will mean pasting each piece of HTML to a separate spot on your page.
One final comment regarding the HTML that the form generates. The generator form creates the mouseovers using span tags. Netscape 4 does not support mouseovers using this tag and you must use the mouseover link form (setting the link destination to #) if you want mouseovers that will work on Netscape 4.
So now you know what you will need to do, you can now start creating your mouseovers, just don't create too many mouseover images on the same page as each requires approximately twice the time to download of a single image.