You need to make a thea.lib file
This then installs all the needed items so the Thea Browser in SU loads the billboards.
The structure is like this...
/PixeroLibrary
description.txt
info.txt
|
|_Models
|
|_Trees
tree-01.mod.thea
tree-01.mod.skp
...whereby you've a folder containing...
2 .txt files
folder named for the library type (Models for models, Materials for maters....etc)
within that folder a Named folder for branding etc...
within that the model category/type
within that the .mod.thea and .mod.skp file where the .skp is the face me billboards