(This tutorial applies to both Ariel and Batya.)
1. Enter the title
2. Add the content
3. Choose slide layout
4. Upload the image or choose from the media library
The slide order is based on the published date. There is not a setting for order. The best way to change the order would be to change the publish date. In each slide, go to quick edit and change the date and time. The more recently posted slides will show up last. The older slides will show up first.