I'm sorry to hear you are experiencing trouble using the fs•texture palette.
How exactly do you try to use(install) it?
Please be aware that thefs•texture palette is an ordinary AE-project-file (*.aep) and not a plugin or script.
To use it you can either import the file "fS_TexturePalette_v03.aep" into your current After Effects project (Ctrl/⌘+I) and use the comps located in the folder Textures>comps as Matte/Blending Mode for other layers within your comp.
Or you download the plugin Ray Dynamic Texture from aescripts, for which this texture palette was originally designed - and I do highly recommend it, it simplifies the workflow immensely.
This video will guide you how to use the palette with Ray Dynamic Texture: