I already filed my taxes jointly with my husband on an ammend return and do not need ny existing filed returns revised for filing. how can I delete them?

Do not delete any return you filed with the IRS - doing so can be a mistake it you or the IRS need these figures in future.  

An amended return does not change your whole return - it only changes certain items, and if the IRS needs to see the original return, you must have it available.