By default, Featured Articles PRO will allow you to create sliders having slides only from regular posts, pages, images and custom post type slide implemented by the plugin.
If you want to create sliders from other registered post types on your WordPress website, you will have to first manually allow them. By allowing a custom post type into Featured Articles you will allow that post type to be used as slides and you will also enable publishing sliders into dynamic areas on the allowed post type archive pages and single post pages.
Allowing additional custom post types into Featured Articles is done from plugin Settings page under tab Settings from option Custom posts. All you have to do is check the post types that you want to allow and save the settings.