The theme maker should have provided you with the information you need and/or a forum for asking questions about their product. This is what a good company does. What did they say?
It’s possible there is a plug-in that controls the slideshow. If it is not placed on the page by a widget, perhaps it is hard-coded into the template itself and you would have to use the editor to find and change what it is doing (again, instructions should have been given about how to use the theme features when you bought it).
Are there special theme pages provided with this template with instructions, added fields that control your slideshow?
Try troubleshooting your slideshow images by right-clicking on an image and seeing where it is being stored. Or, look at your media library, are they there?
Do you know how to find your widget settings?
You can troubleshoot widgets by removing them (move them to the lower section, that preserves your settings) and adding them back one by one. Same with your plug-ins, deactivate them and add them back one by one to troubleshoot those.