In order to help you we would need additional information. Post the image so that we can see whether the skyline includes mountains, trees, buildings, etc. In addition, provide the exact version name of Photoshop you are currently using.
Are you asking how to add a landscape image from CC Libraries into your Photoshop project? Or are you in the process of adding an image from CC to Photoshop? Or are you asking if you can add a CC Cloud image into a landscape Photoshop image? Or are you asking if you can add a landscape image into Photoshop?
We definitely need more I do and clarification to help you solve your issue.