Here's a simplified tutorial for Poser's Runtime structure for anyone new to Poser who's reading this thread.  There are only three basic rules to follow.

There are three sub-folders under the main Runtime folder:

Geometries
Libraries
Textures

Rule #1 - Never touch anything in the Geometries or Textures folders.

Depending on what your content comes with, there are up to 9 sub-folders under the Libraries folder, which correspond with the categories in Poser's Library:

Camera
Character
Face
Hair
Hand
Light
Materials
Pose
Props

Rule #2 - Never touch any special sub-folders your content may add to the list above.

Rule #3 - How you organize your content within each of the sub-folders above is entirely up to you.