You can add parameters to your Java Action so you can easily pass data into it. These values will then be available to use in the action. Now you have the data, it would be a case of finding and following the documentation for XMLSlideShow as to how to add them to the PowerPoint document itself.
https://docs.mendix.com/howto8/logic-business-rules/extending-your-application-with-custom-java/
https://poi.apache.org/components/slideshow/xslf-cookbook.html
Good luck!