I can't find any information on this issue, but I'm not seeing any way to create subfolders in the Assets view of the control panel. I just see all of my images with no folders. Is this feature restricted to paid versions?
What you see on the left in the Asset section, are asset-sources and their subfolders. You can configure them in
Settings -> Assets -> New Source.
In this example,
Cars are asset-sources:
You can add subfolders to each asset-source (and each other subfolder) with
Rightclick -> New subfolder.