The base image is created as a complex multilayer composition with gradients, blur and glow effects. Creating it is beyond the scope of this answer. But you get the grain because it happens to be nearly the same that I have made one case earlier.
At first the grain and unfortunately also all other fine details were removed from your image with smart blur:
The layer was duplicated. The top layer got full white layer mask and the bottom layer got a curves adjustment layer:
The mask of the top layer has got max intensity black and white pixel grain and the curve of the bottom layer has been tweaked to make the grain to become visible as brightness variation in some brightness areas:
The grain in the mask is this: