After the slideshow is enabled on your WordPress gallery, the toolbar will display pause/play UI elements for the slideshow. Assuming you have keyboard navigation enabled, you can also use the space bar to control the slideshow.
The slideshow works once the lightbox has been opened. You can set it so it start automatically or when the user manually click to start the slideshow.
We have created a demo gallery that utilizes our slideshow addon. Autoplay is not enabled on this slideshow, so you must click the Play button for the slideshow to begin.