If you click the Copy button in the toolbar when there is no Destination window (e.g. you only have one file display open) then you should see a Select Destination Folder window like the one below.
Are you seeing that?
Do you have just one Opus file display open? If you have more than one then the files will be copied to the other one. (See the MultiListers video in the Tutorials forum if you don't understand how that works.)
