To change the cover of your story, from a computer, go to "my works," which will be on the drop-down menu that is on the Wattpad bar if you hover over your username. You will find your work there. Click the image of the story and a window will pop up. It will have two choices. "Edit" and "Create." If you choose "edit" you can upload your own cover from your computer. "Create" will take you to the Wattpad cover creator, where you can make a cover from the limited images they have.