I have a product completed, but it opens on 10th slide and no the first.
I hope all is well. I'm more than happy to help you with this one.
You can rearrange the order of the slides in Story View. You can drag and drop the slides where you want them to be. Make sure the slide that you want to start with when you preview is on the topmost of the Scene.
You can also take a look at this guide.
I hope this helps. :) Cheers!