Go to “Programming” > “Selections” and click the selection you wish to delete as if you were going to make changes to it. At the bottom of the selection editor is a link to “Delete Permanently”. Click that link to delete the selection. You will be prompted to confirm the deletion.

If you see text that says “Not Available for Deletion”, then you cannot delete the selection either because it has been programmed in a screening or because it has been nominated for an award.