Open iTunes and just drag the files to the Library section. (Install a Perian for your QuickTime Player if you can't open MP4 files with QuickTime Player). The below steps would show you how to burn MP4 to DVD Mac with iDVD if your MP4 files couldn't play correctly on QuickTime Player: However, if your MP4 files couldn't played on QuickTime Player correctly, you may need to turn to some other tools to convert MP4 to DVD Mac with iDVD.
Go to 'File / One Step DVD from movie.' from the menu bar.