click on Author DVD, on the right pane, there will be a bunch of options that you can check adn uncheck (checked ones will be copied onto the DVD. Use the left pane to navigate to differnt folders (chapters, menus etc) so that you can take out the audio there as well (clicking on a differnt folder changes the options on the left.
Note that the menu will probably still say spanish/french, etc,. its just the correlating audio tracks will be absent.