I can help if you have specific problems. But it sounds to me from your message that demo 3 comes up, but you don't know what to do with it. Correct me if I'm wrong. If its the case that it comes up ok, but you just havent read the docs, then you're on your own

You need to read a Bunch of stuff before you can get anywhere. These demos are testbeds for our General ideas about the game models, and aren't all That playable by themselves. For demo 3 read everything in the summary below the download. Backing off and starting with the demo 2 doc first might be best.

I just bumped up the demo 3 thread, which has some more info.