You can only edit your photos. There's a cog icon under every photo you uploaded. When you point it with your mouse cursor it'll show more options, including "Edit Photo" and you'll be able to change:
- Photo title
- Add photo to a weekly theme
- Put photo on sale
- Add or remove watermark
On the Editing page you'll be able to delete the photo. Be careful though. Deleting a photo is irreversible. You'll lose all the likes, comments and views assigned to this pic. You will be able to reupload it later, or put another photo in that place.