You're not quite getting the point. The
highslide.css file is almost entirely dedicated to styling the
enlarged images. There is a skeletal
highslide-gallery class in there, but that's just to provide a minimal thumbnail display to support the bare-bones examples. It's not really part of the Highslide JS package.
The Highslide JS script doesn't produce the thumbnail table. The assumption is that anyone using the script will be creating his
own thumbnail table, with its own styling, captions, and so on.
If this is beyond your skill level, you might be better off using an application that produces this for you. Take a look at some of the sample albums on this page:
http://jgromit.com/matrix/. They all use Highslide JS to display the enlarged images, but the thumbnail page is produced by a skin for the jAlbum application. The
Maps & Metadata album, for example, shows captions under the thumbnails - the
Beveled Thumbs album shows them to the right of the thumbnails. These albums are all produced by the application - no manual coding required.