Modding help needed

[PajamaJams]

I know how to get to the KSP parts folder, but I'm confused. Am I supposed to put the .zip of the mod or the folder itself?

[mythbusters844]

Not sure what you're saying, but you have to put the folder in the .zip in GameData. There are installation instructions too, make sure to read them.

[Gaarst]

You have to extract the .zip first.

If the extracted folder is "GameData", then just merge it with KSP's GameData folder.
If the extracted folder is the name of your mod, then take a look inside it: if it contains a folder named GameData inside, then see above; if it contains just random files/folders, then just drop the extracted folder inside KSP's GameData.

Normally, inside your GameData folder, you will then see the Squad folder and the folder of your mod (possibly other files on their own also, especially ModuleManager files).

CKAN automatically installs mods if you want, but it is known to sometimes cause issues with your install.