Tutorial Confusion - Model not showing up?

So I've made a simple cube jbeam based off of this tutorial here http://wiki.beamng.com/Introduction_to_Vehicle_Creation but I can't seem to get the model to show up in-game. I'm confused about the flexbodies portion of code, and this is what I had put down;

"flexbodies": [
["mesh", "[group]:", "nonFlexMaterials"],
["cube_body", ["cube_body_g"]],
],

See, I'm not sure what each parameter means, as the tutorial confuses me at this point, and says the "first parameter" is...

Tutorial Confusion - Model not showing up?