Hey,
as I wrote in this thread: http://www.kriesi.at/support/topic/cufon the easiest solution is to rename an existing font file (like cardo.font.js to cardo.font.js.bak) and renaming your new font file to cardo.font.js. Then select "Cardo" font within the backend.
If you know how to delete sql database entries you've another option - first open up options.php located under includes\admin_option_pages and add your font to following code:
'Bevan'=>'bevan',
'Cantarell'=>'cantarell',
'Cardo'=>'cardo',
'Droid Sans'=>'droidsans',
'Inconsolata'=>'inconsolata',
'Josefin All Characters'=>'josefine',
'Josefin Common Characters'=>'josefine_small',
'Kreon'=>'kreon',
'Lobster'=>'lobster',
'Molengo'=>'molengo',
'Reenie Beanie'=>'reeniebeanie',
'Tangerine'=>'tangerine',
'Vollkorn'=>'vollkorn',
'Yanone Kaffeesatz'=>'yanonekaffeesatz'
Afterwards delete the Broadscope settings from your database and the new font should appear in the admin panel...