Enter Trash page from the left sidebar, under Manage.
Select the terms/URLs you want to perform the action on, and from the Bulk Actions menu, select if to restore or permanently delete Terms or all URL data.
If under a URL in Trash there are also active terms (terms that are not deleted and still being tracked), you will not be able to delete the URL. You can still select and permanently delete terms under it.
*From Edit URL page, in Delete/Restore Terms tab you can select terms to delete or restore (there is no option to permanently delete from this page).