Poiyomi Toon is a shader. You "install" by importing them into the project, just like the VRC SDK package and your model. You port these after you import the VRC SDK and BEFORE your model.
Oh, crap, I forgot, the chest wasn't properly assigned. Thanks Unity. Go to the model, and in Inspector on the Rig Tag, press Configure and reassign the Chest bone to the Chest in the right hand menus.