We have an assortment of layouts that allow you to put captions on each photo so that you can have different text for each slide. They reside under the Slideshows category in the Ripl layout catalog. To reach the catalog, you can select a post from the Home screen or start a new post from the "+" button. You can then access the layout catalog by tapping the More layouts box on the Customize step, which will take you to the Slideshows category.
In the desktop version of the Ripl app, once you add more than one photo to a slideshow layout, arrows will appear under your post's preview, which will allow you to switch between slides. You can add more images by clicking on Media on the left side of the screen. You can add text for each of your slides by clicking on the Text option.
This blog post also walks you through the different types of layout available in the Ripl app.