Looks like the slideshow folder is in /config/fancymenu/assets/ — FancyMenu only scans /config/fancymenu/slideshows/<your‑name>/. Move slide1 (with properties.txt and the images/ folder) into config/fancymenu/slideshows/ instead of assets/, then reload FancyMenu (Customization → Reload FancyMenu) so it re-reads that folder. After that the “Choose Slideshow” screen should list your spoglite slideshow.
For reference, the official setup is described in the Slideshows page.