If you bought this asset pack on the Unity Asset Store, you can use the package manager to install it. If you got it on itch.io or Gumroad, then you will receve a .unitypackage file, which you can install via Assets -> Import Package -> Custom Package. When you download this pack from any storefront, all the assets will be contained in the Toon Shaders Pro folder.

Using the shaders

Create a new material and pick any one of the shaders in the pack from the drop-down list at the top, which will be in a subfolder named Toon Shaders Pro. You can then tweak the settings of the shader and attach it to any object.

If you want to use the shaders with a terrain, pick the Toon (Terrain) shader on your material and attach it to the terrain’s material slot. This will automatically pull textures from the terrain data and use these for terrain rendering.