To delete, go to your home page (little house icon, upper right), click on "pictures" along the left side of page, and there will be a display of all your pictures, each with a delete button next to it.
The site's not going to fix your rotated picture, you will have to do that and re-upload it. Your camera has an up/down sensor in it, and marks each photo with "this-side-up" metadata. But if the camera was sideways when the picture was taken, the actual image is sideways. Your photo browsing software checks the "this side up" data and displays it correctly for you. The web software does not.
So you need to open the photo in very simple editing software - the Paint that comes with Windows is fine - and if it displays sideways, rotate it and save it. Then upload that.