To install this voice guidance speaker in Marble, copy the entire directory to the audio/speakers/ directory in Marble's data path.

For example, if this directory is called 'MySpeaker' and you want to use it on the Nokia N900, copy the directory with all files to /home/user/MyDocs/.local/share/marble/audio/speakers/MySpeaker

Afterwards start Marble on the N900 and press the routing info box (four icons on the bottom) for two seconds with the pen. Enter the configuration dialog and choose the 'MySpeaker' speaker.

Check http://edu.kde.org/marble/speakers.php for updates and more speakers.