Question what is the process to add GPU Instancing to store bought shader?

hello

im having trouble figuring this out for years

in simple, what do you do, like actually make sure is added to shader code, to make your shader support basic GPU instancing, complex GPU instancing (multi-material slot matching??, texture arrays??), etc?


I am trying to convert this shader to do it:

https://assetstore.unity.com/packages/vfx/shaders/psxeffects-132368

because somehow THIS one supports it:

https://assetstore.unity.com/packages/vfx/shaders/realtoon-an-anime-toon-shader-65518

which boggles my mind.

please help!!!!!