In Cinema 4D, "Sky Presets" typically refer to either pre-configured Physical Sky settings or HDRI (High Dynamic Range Image)
Greyscalegorilla is the industry standard for C4D lighting. While their Plus library is paid, they offer a robust that includes several HDRI skies. Cinema 4d Sky Presets Free- Download
So, you’ve downloaded a pack. Now what? In Cinema 4D, "Sky Presets" typically refer to