Playing home videos to smart tv app

I have a brand new LG smart TV which has Apple TV as an integrated app. How can I share my iMovie home videos for my iMac to the AppleTV app in the TV? From the iMac, I’ve already saved the finished movies as a file and imported them to the Apple TV app - they do appear in the library in the AppleTV app on my iPhone, but they don’t appear in the TV app. Home sharing is on and I’m using the same Apple ID - is there a step I’m missing or is this a limitation with the AppleTV app on the Smart TV? Is it possible to do this without the separate AppleTV hardware? I’m trying to use this method as steaming from my iPhone to the TV via screen mirroring is a bit fickle. Thanks much for any advice.