Extract the mod files you downloaded earlier into the "MyMods" folder you just created. Make sure to extract the files directly into the folder, rather than creating a subfolder.
Save the file and close it.
mod/MyMods/mod.json
To activate the mod, you need to create a new file called Victoria 3.options in the game's root directory. Open this file in your text editor and add the following line: victoria 3 install mods manually