Adding files format to forum

hello, i have question about forum. i want to add some extensions of files which users can upload in posts on forum and i want to ask where i have to change that? only in index.php or somewhere else?

files/.htaccess ??
forum/includes/files.php ??

i try to upload font with .ttf extenstion and added ttf in forum/index.php and in files/.htaccess (addtype application/octet-stream .ttf) but cant upload font to forum. any one can help me solve this problem?

forgot to say, im using 6.2.0

so i must add ttf in one more file
incfiles/lib/class.upload.php

thx for help