One aspect of ENB need to be understood is - weather & shader files required by ENB can located in TWO places - game main folder, or inside folder. Mixing old / foreign ENB files is a recipe to disaster. Unfortunately a lot of guide / description forgot to mention this part.
The following process mostly refer to Oldrim's ENB.
Most info may only applies on Oldrim ENB. ENB RANTS, because seen way too many people seems to unable to get this simple thing right.