Only then, this guide is helpful for you! Also – a lot of modders give a little tutorial on how to install mods.
The modder will tell youin his description if the mod needs to be installed manually.
Generally, you do not have to install mods manually. While going through the Steam forum I found several topics with people questioning where they have to put the mods, and how to install it. On mod.io we can sometimes find interesting mods that require a manual installation.