This happens because of the way your camera encodes your pictures. As a result, the Sitebuilder is not able to recognize the orientation tag which dictates how your picture should be displayed.
A way to correct this is to upload your image to an image editing program such as Picmonkey http://picmonkey.com and simply resave the image. This will encode your picture with the correct orientation tag that is readable by our Sitebuilder.
You will need to re-add this back to your File Manager and re-add to your page.