Hi @alriksson,
So sorry, I forgot to subscribe to the plugin’s forum as it is a recent release with no topic yet. I just fixed this for any further topics in this forum.
About your question, there is no shortcode support yet. The lightbox is loaded only if it picks up on images within the content. In the current version (1.0.0), the plugin picks up on the images globally in the page, accordingly to the selector (more on this in the next paragraph).
As of now, it does not officially supports ACF. However, you may get it to work fine provided that you input the correct css selector in the settings (under GENERAL > MEDIAS > Selector). Note that the images must be wrapper in an “a” tag (an hyperlink) to be shown in the lightbox and the final element of the selector must be either “a” or a class or id within the actual “a” tag that wraps the image in a link.
Also, you would need to make sure that any other lightbox plugin is not active at the same time or it could create conflicts.