Unfortunately, that's how this theme was built. 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. You can always remove this slider and create a slider module. https://urjtechhelp.zendesk.com/hc/en-us/articles/115002545653-Add-a-Slider-of-Posts-Images-Videos-or-Text. You can reorder these slides with drag and drop.