So lets go on buddy...
...as You could see on the picture above, we have a few steps ahead.
1) Activate MIST in the Render Layers / Passes as could bee seen in the center of the image.
2) Choose the camera and activate MIST in the Camera / Display section. Now You are able to see the yellow line near the camera which shows start and end of the mist.
3) Now select the values for START and DEPTH in the World / Mist Pass. The line of the camera will follow accordingly.
4) Render your image.
5) Finally, open Compositor in Node Editor and build the nodes like me - the important changes are in the RED rectangle. The Node I added is the Add / Color / MIX.
6) Render your image AGAIN.
Hope it helps, buddy - sincerely, Jan