You can delete a destination from the edit destination page. First, click on the destination you would like to delete.
Click on the trash can icon shown here to delete the destination, you will be shown a popup where you will confirm your decision to delete.
Click "Yes" to confirm your deletion, or "No" to abort.
If you channel is "live" you will not be allowed to delete any of your destinations. You will first have to stop the channel from the "channel configuration" page and then return to this page to delete the destination.