Adobe have recently released a new feature in Adobe Photoshop called Sky Replacement. This tool is designed, however rightly or wrong, to help you replace the sky in an image.
If you haven’t learned Adobe Photoshop’s various ways to blend images then it can be useful but only to a point. What I’ve found is that it isn’t as all singing and all dancing as you might expect. That it’s still far better to put some time and effort into properly learning Adobe Photoshop.