Hello there,
Yeti is a 3rd party commercial plugin for Clarisse developed by
Peregrine Labs. Once you installed Yeti's Clarisse plugin, a new Yeti Fur geometry becomes available. This geometry is created like any other geometries in Clarisse. You just have to set the Filename of the Yeti Fur geometry to a Yeti fur cache to load the fur in Clarisse.
The best is to directly contact Yeti's support since they develop this product.
Thanks,