I implemented Highslide JS in a Freeway site - http://www.frenchwineroutes.com/ Click the Sitemap, Privacy Policy or Terms & Conditions links to see it in operation.
It is fairly straight forward, and there are a lot of customisations which can be made. Refer to the Highslide JS website for further customisation options.
See 2 screengrabs below of where to input the required code to get it to work:-
I have added my own customisations in the second entry, but you can at least see the principal.
I just tried using the HighSlide editor to create a gallery, easily uploaded it, they provided the embedded code - it was amazingly easy I thought. I not only donated to them, but can’t wait to try out more styles. Reasonably priced, and easy to use with good looking results. Can’t beat that!