Hi, I had to delete the 500 x 750 poster you added since it was distorted. Distortion happens when you change the aspect ratio of an image without first cropping. If it's not possible to crop the image to a perfect aspect ratio, it's fine to keep a poster that is slightly off in that regard.

In this case you can see the original image (not distorted) next to the distorted version. You will notice that the distorted image is too thin, it has been squished. Before adding more image you need to figure out how your image program works. It's usually a setting about preserving the aspect ratio when re-sizing. You should also take a look at our Image Help section. Thanks.