Go to dashboard>> slider >> add new >> set title and other details >> set featured image from the right side panel >> click on publish to save changes
Repeat this procedure to add more slider images
If the slider doesn’t appear please disable all your plugins and check if it works.
If it still doesn’t appear then please check if you have setup the static front page.
If none of them works then please contact us on [email protected] with your wordpress username and password along with your website link and we will see what is causing the problem.