1. In the menu bar, go to Insert>Image Object>Rollover Image.
2. Specify the original image.
(The image you want to see without rolling over)
3. Specify your rollover image.
(The image you want to see when you rollover the previous image)
4. (Optional) Specify the extra options.
(Link it up, Add an alt property, or choose whether or not the image will preload on page load)