Can someone tell me how to delete a LingQ?
Go to the Vocabulary Page and delete any LingQs you want. As a paying member you can do Bulk Deleting, as a free member you have to do one by one. There is also the option to delete an individual LingQ when you have the widget open.
(There is really not much point in deleting LingQs when you are a paying member, unless they are incorrect.)