Steam

Its steam workshop, so if you are not familiar, all you need to do is own TTS on steam, download it, then go to the steam workshop page for TTS and then yeah its basically like you said from there. Any single thing you can find on the steam workshop can be downloaded for free and loaded into TTS. I have played hundreds (not even exaggerating) of games on TTS and I have never had an issue finding a tabletop game I was interested in on there.