Select one photo by clicking on it.
Then, do CTRL A to select all.
Then hit Delete.
A message will come up asking if you want to also delete them from your hard drive. Choose wisely, as deleting them from your hard drive will get rid of them permanently.
If you choose not to also delete them from your hard drive, they will be deleted from the Starter Edition Catalog, but will still be on your hard drive and you can add them back into Starter Edition as needed.