Slideshow to static image

There is no option for that. You have to tweak the code a bid and add the slider code/shortcode in the place, where the homepage image is loaded. Somewhere around here https://github.com/mpeshev/Shell-Lite/blob/master/front-page.php#L40.

I’ll strongly suggest you to use Child Theme https://codex.ww.wp.xz.cn/Child_Themes if you are going to modify the original theme.

Good luck!