Do you have PhotoShop? I bought these actions/templates from a guy (can't remember the site for the life of me) and you just open the actions in PhotoShop and edit the template then PhotoShop generates the cover.
That's one way of doing it or you can buy some of these e-book cover generators. I prefer the PhotoShop way though because you have more control over the design. Sometimes the ebook cover generators are kind of limited.