Enduser Guide
This guide is for all people who use a ENB that does not support Vivid Weathers and want to make it compatible up to..lets say 90% with it.
You will need to use atleast version 0.262 of the ENB files - even better if you use 0.305+ 
You might certainly be screwed if your enb is so old it just supports version 0.119 or similar because then your shader files could be more or less incompatible.
Lets start this as clean as possible - delete/move all old enb files in your skyrim directory.

This covers files like:
enbseries folder
enbersies.ini file
effect.txt file
all files that end with .fx exept the smaa.fx
enbcolorpalette.bmp or similar
The only enb files that should be left from in your skyrim folder is the d3d9.dll (if you use the wrapper version) the enblocal.ini and the enbhost.exe Create 2 new folders. One containing files of your actual enb that you want to modify to work with Vivid Weathers and one with the Main Files of the Vivid Weathers ENB.
Depending how your original enb is build up you will have all of the .fx files outside of your enbseries folder or inside. 
Make sure to keep them - those are your shader files and should not be overwritten. If your enb does not come with a enbseries folder, create it. 

1. Go to the Vivid weather enbseries folder and delete following files:
effect.txt
effect.txt.ini
enbbloom.fx
enbbloom.fx.ini
enbdefs.fx
enbeffect.fx
enbeffect.fx.ini
enbeffectprepass.fx
enbeffectprepass.fx.ini
enbsunsprite.fx
enbsunsprite.tga
enbsunsprite.fx.ini
Shader Functions Folder
We wont need them anymore.

2. Copy everything thats left into the enbseries folder of your original enb and overwrite all files that might be in there.
Make sure you copy enbhelper.dll - this makes your original enb weather aware!

3. Open the enbseries.ini file of your Orig. enb. Now it gets tricky.
Look for the [WEATHER] Section. Does it exist? Good! you are lucky. 
Set EnableMultipleWeathers=true and continue to step 4.

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Is there no [WEATHER] Entry? Well.. you are screwed :D Your enb is so old it never seen the Update for ENB weathers a few years ago.
From this point on you should think about swithing to another enb or continue at your own risk:
Add following section below the [COLORCORRECTION] section: 
[WEATHER]
EnableMultipleWeathers=true
Save the file. And copy all the ENB files and enbseries folder over to your skyrim directory. Make sure you use atleast enbseries 0.262 and start the game.
Wait till the main menu has been loaded and press Shift+Enter to open up the enb menu. On the upper left corner you will see "save configuration" Press that button and exit skyrim.
Your enbseries.ini now contain alot of more entrys and continue to work from iside yourskyrim folder from now on. continue to step 4.
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4. You will need to change the line IgnoreWeatherSystem=false to following sections of the enbseries.ini
[BLOOM] (50/50 it looks good in doubt leave it be)
[LENS]
[ENVIRONMENT] 
[SKY]
[VOLUMETRICFOG]
[PARTICLE]
[RAYS]
[CLOUDSHADOWS]
[VOLUMETRICRAYS]
[PROCEDURALSUN] (50/50 it looks good in doubt leave it be)
[MIST]

5. Change following values in the [TIMEOFDAY] section
Enable=true
DawnDuration=2.0
SunriseTime=7.5
DayTime=13.0
SunsetTime=18.0
DuskDuration=3.0
NightTime=21.0
Notice: Dusk and Dawn times only apply if your original ENB has set DawnDuskEnable=true. Never set DawnDuskEnable=true on ENB's that do not support those dawn/dusk times by default.

6: You need to set following effects to true in the [EFFECT] section
EnableMist=true

7. Save and copy all of the enb files of your modified original enb to your skyrim folder. Run skyrim and go to the Vivid weathers MCM menu. Enable Customizion and set your bloom Level to a value that suits you and the ENB.