Nornal Mapping - How to export it to Gimp/Photoshop

Thank you so much for this! This has helped me out heaps! So when adding textures, could you show me what you did and how you did it? Like what is a Diffuse Texture? Is it a UV unwrap? I’ve a UV Layout and its all unwrapped, l just don’t know how to add textures to it!

Like how did you do the textures? Was it with the normal UV layout thing or what did you do? Could you please demonstrate how to do it?