Manual Installation: Download and install 7zip. Once you have downloaded the mod, open the archive (.7z, .zip or .rar) with 7zip, and click extract. Extract the files so that the files (esp, bsa, etc.) and the folders (meshes, textures, sounds, etc.) are in the Skyrim data folder (\Games\Steam\SteamApps\Common\Skyrim\Data). Activate the mod through your preferred launcher by ticking the checkbox next to the esp/esm.