How do I create a navmesh?

I just want a basic idea. I created a bit of a scene and then hit “generate navmesh” in the scene tab in (blender 2.8 armory 0.6) – but nothing happens. I figure I must be doing something wrong. Any suggestions?

There is example here, check it out :smiley:

Except that doesn’t actually tell me how to do it. It’s already pre-made in that example.