The My DAZ 3d Library is located in public documents on a PC and is the default library used by DAZ Install Manager (DIM). I leave that library alone and let DIM manage that library. I install all content from other sources in My Library.

DAZ Studio supports both DAZ Format libraries and Poser Format libraries. The My Library and My DAZ 3d Library are folders that contain a DAZ Format library. Inside the folders for these libraries you will find a Runtime directory which is a Poser Format library.

If you get a vendor zip files with only a runtime with geometries,textures and libraries etc you can merge this into the Runtime folder under the My Library directory.

DAZ format products frequently also contain a Runtime folder, sometimes under the My Library or Content directory. This Runtime usually only contains Textures. Most DAZ Format products still store their texture files in the Poser Format Runtime library inside one of the DAZ Format folders.