Hello there!

For the model plugin to work you have to first import the model file (glb/gltf or obj) you want to use into your project's files folder. 

Then in the model object's properties you set 'File name' to the name of the file you just imported. Now the model should actually show up in your scene when you run it.

Let me know if you need further assistance. There probably should be an example file for this in the future.