No worries! Thanks for clarifying – I get it now. With the principled BSDF the fresnel component is built in. While this is nice because reflections automatically look more realistic, the negative is that you can’t customize the fresnel (as I do in this video).
..where i can put fresnel node ?
To answer your question, you don’t need to add it anywhere. It’s already part of the principled BSDF.
