Photoshop is a very popular program. It is the ultimate solution for most of the design work. However, in order to create an ebook cover on photoshop you need photoshop skills. It takes months, even years, to master photoshop skills.
Apart from PHOtoshop, there are other designing programs as well, for example illustrator, GIMP etc. However, all of these program require specialized skills.
If you are publishing your ebook on Amazon Kindle, you don't have to do the cover. Just upload the image you want on the cover and run cover creater, you will have amazing designs in one minute.