Ash here from the Shopify team. Welcome to the Shopify Community, and thank you for posting your question in here!
I'm happy to help out and provide some steps on adding a slideshow to your Shopify site. In order to make sure I provide you with accurate instructions, could you please reply back here and let me know what theme you're using? Since each theme is unique, the steps may vary slightly from theme to theme. Once I know what theme you're using, I'll get some screenshots and steps together for you.