This is a site called CANVA which
allows you to create many things
including covers and promotional
materials for your book.
I would suggest that you play around with it for a little while and get used to it before trying in earnest to design your cover.
This is PIXABAY where you can access photos, vectors and illustrations that are free to download and free for commercial use. (Just be aware that unless you alter the image you run the risk of others using the exact same image).
I will follow this post up during the week with one on how to navigate the Template on Createspace.
(These are meant to guide you, I advise that you play around with the tool and be aware that some images on this site do come at a cost)