Select the CD/DVD drive device in the left-hand sidebar, then select from the "File" menu, "New" > "Disk Image from [device]" where [device] is the CD/DVD partition selected in the left-hand sidebar (should be the first indented partiton below the CD/DVD device listed there).
Then, set "Image Format:" to "DVD/CD Master" and "Encryption:" to "none". Select a place to save it, click "Save".
Then, to burn the copy, simply insert blank media (DVD-R disk), select the image in the left-hand sidebar that you just made (if it isn't listed, simply drag and drop the actual CD/DVD image file into the left-hand sidebar), and click "Burn". The copy should be fully bootable.