Fairly early in our vILT Adobe Captivate 12 classes, we teach learners how to work with slides and blocks. To add blocks, visit the toolbar at the left of the screen and you'll find tools that allow for text, images, videos, and interactive components such as buttons and data entry fields.
One awesome feature in Adobe Captivate 12 is the concept of infinite slides. Because Captivate is now a 100% responsive eLearning development tool, there is no such thing as a slide height. Add as many blocks as you want to a slide, and the slide gets taller and taller.
In the image below, I've added some text blocks, image grid blocks, and a few other items.
Notice that when I switch to mobile preview, the content reflows to fit the device screen size and, as the learner, I simply swipe to move through the content.
Check out my video demonstration of infinite slides.