Navigate to
your "Gallery" and click on the photo you wish to delete.
This will open it in larger size. Click on
"Image Tools" at the top. Then select "Delete image" from the menu.
At the top will be a grey delete box with a check box - and the following
"To delete this image, check the box to the left and then click the 'Delete This Image' button below."
Check the box and click on the button. This will delete the photo.
I don't know of a way to
replace an image since they're all tagged when they arrive, so you can't just overwrite it like you can on your home computer. Good safety feature since most of us use the same tags over and over i.e. DSC00001.jpg etc.
Good luck!