First, you need to import it to iTunes. From there, a playlist should be created...if not, then you need to create a playlist for the audio CD you've just imported. Once that's set, you can burn the CD from iTunes using that newly created playlist.
Or you can go to disk utility and go to file in the menu bar and then go to new and then disk image from (name of disc). Then once its finished go to images and then burn and select the image that was created and wait for it to burn.
