Thanks for trying it out again! It's not your fault, it is currently impossible to bring assets into the world editor. I'm waiting to have the asset editor a bit more fleshed out before connecting the two. Hopefully the next release will include that functionality.
As for attaching a player to a model, you're right that it doesn't exist yet, that's probably gonna come with the next update as well.
I will definitely make some tutorial videos at some point. Once I have a stub of gameplay working I'll record a video showing the full end-to-end workflow: creating some textures, building a room, creating some assets, maybe a simple player model, and bringing it all together.