you may need to check the related lightbox script’s main site (the one you picked) to see the actual method to do inlined content. Most (if not all) have a way to do inlined html lightbox. For example, i am using nivo of this plugin and although this plugin doesnt make mention of inlined html the underlying script supports it perfectly. The original script maker for nivo (not this plugin author) had a few bugs and forgot to include a method to close the popup (besides the “X” at top-right — which isn’t always ideal since for html inlined code i’d prefer a button for the user to click on instead) so i added the enhancements and dequeued and enqueued the custom script back to this plugin to make it easy for when this plugin updates it will continue to use my “fixed” version of nivo instead. Yay, for me.
Anyway, im sure the script you picked in this plugin supports inlined html. You will have to check the related site to see how its done.