The catalog for HD flowers libraries are not yet available, you can't use them directly in the library browser because the browser needs thumbnail images and additional information that is not included on the .max files.
We are pending to receive thumbnail images from 3DMentor to finalize it, as soon as we have this information, we will release a updated version of HQ Catalog supporting all flower libraries.
HQ Plants libraries is a product maded by 3D Mentor, we are only distributors of their products, however to facilitate the integration with forest we create with HQ Catalog add-on that should be updated for each new published library.