Featured ads in a slideshow

Do you mean this Carousel Slider https://www.ads-software.com/plugins/carousel-slider/? It does not seem to support custom post types (other than WooCommerce products), so i do not think you will be able to do that at least not without some custom programming.

It does support normal posts though if there is a way to get WPadverts generated ads to register as posts?

It would be best to ask their support, they do know their code and should be able to tell if there is some filter or action you can apply to use a different post type than “post”.