How to set active state for thumbnail in CMS slider (Flow Ninja)

I’ve tried to use the clonable CMS Thumbnail Slider from Flow Ninja. The only thing I haven’t been able to get to work is the ‘active state’ interaction for the thumbnail (where the thumbnail is highlighted). I’ve attached the RO links for both their original template and my attempt to get it working after cloning their template. I can see that they’ve set transition effects on the thumbnail slider item, but I can’t figure out where they’re actually triggering the active state.

Flow Ninja’s Clonable RO: Flow Ninja’s File

My attempt at cloning and using their template RO: My File