Again, in this video he is using localhost. We are using the Ancient Brain server, where you can upload your own 3D models. Search for OBJ files that people have already uploaded. You can get OBJ files from sites like free3d.com.
For you: Go to "My uploads" and upload a different OBJ and insert it into your World. Or just directly reference the OBJ of another user. The World also adds background audio. You can upload your own audio and make that the background audio.