My suggestion would be to just download it again and install it. It will not work unless you have your license number but most people know that and there is a link to find it even if you don't know it. But these are the full versions of the software they just require that you have your license number to activate it
Make sure that you install it and it should show up in your applications folder immediately after and it should start if you click on a quickbooks company file. they are usually in the documents folder.