To delete one or multiple photos at once, go to the main Photos page. We like to filter our photos first, but that's optional. Select the "Delete" button, as seen below, and an "X" will appear at the top left for each photo.
Selecting the "X" will change the icon to red, denoting that the photo will be deleted after selecting the "Delete Selected Photos" button.
Note, you can also select the "Select All" link in the dropdown, which will mark all photos on the page you are viewing.