I haven’t found an easy way to get models from 3D Warehouse into my library.
When you go to 3DW from SU, you are offered to download direct to your working file or elsewhere. If I try to navigate to my library using Mac’s Finder, I cannot get there as the path is not shown. The only way I can do it is by putting in the Download folder first and then transferring it. I guess there is probably a way to get it from your working file to the library but that too would be a double process. I don’t understand why you are not given a 3 way option to download: either to working file, library, or other, and for the system to “know” the path to the library automatically.
But maybe I am doing this all wrong and I just haven’t found the proper way to do it?