Belated welcome to the forums!!!
For most mods, it's as simple as unzipping the .zip into a folder called Gamedata (that's where the mods go)
However, have a look in the mod's folder. If it has another Gamedata inside it, then you should put the contents of that in the main Gamedata.
You can keep the unextracted .zip if you want, but I usually delete it as it doesn't do anything and just takes up storage space.