Ok this is instruction for workshop mods. This i know work for Crusader Kings II, Europa Universalis IV and Warlock II. I know it works for other game, but you could try it alone.

This instruction is the same for CK II and EU IV:

01. Download addon Tampermonkey (if you use Chrome) or Greasemonkey (if you use FireFox).
02. Install this script for your addon above Gaddons Download Button: http://userscripts.org:8080/scripts/show/131355
03. Go to workshop page of mods
04. Now you will have DOWNLOAD GREEN BUTTON, click it.
05. Now it will redirect it to new page
06. You will see in the center of page line Start Download, click it
07. Wait a little and then you will start downloading
08. Some files will already be packed in .zip format, but someone will not have format
09. You just change format adding it at the .zip at the and of name of file
10. Now you can extract mod.
11. When you extract mod it will give error because he can't extract one file from zip (descriptor.mod). Don't worry that file is not needed.
12. Put all files from extracted mod in one folder and name it. For example Awesome_Mod.
13. One more thing you need to do. Now you must create .mod file. Its really easy. Just open Notpad:

• You need to write just two lines or three deepens on you
• name="WRITE SOMETHING HERE" -> The name on mod how will present in launcher
• path="WRITE SOMETHING HERE" -> The name of folder where is mod
• user_dir="WRITE SOMETHING HERE" -> The name of folder where is your Save File for this mod (this line doesn't need, and folder will be outside mod folder)

Here is the example:
14. Now when you write all what you need just save it with .mod extension.
15. Put this file (.mod and folder) in \<USER>\Documents\Paradox Interactive\Crusader Kings II\mod\
16. And that's it...

It is a little bit hard in the beginning but you will get used to.