Use the File... menu in Content Manager then. Choose 'Import content files...' and navigate to the location on your HDD/SSD that contains the .cdp and install them from there. Drag and Drop doesn't always work if you don't have your file extension associations up to date.
Use the File... menu in Content Manager then. Choose 'Import content files...' and navigate to the location on your HDD/SSD that contains the .cdp and install them from there. Drag and Drop doesn't always work if you don't have your file extension associations up to date.