When you get new fonts, you can install them using Font Book. When a font is added in Font Book, it automatically appears in the available font lists in your applications and in the Font panel.
-Insert the disc that contains the new font, or copy the font to your hard disk from another location.
-Double-click the icon for the font in the Finder. Font Book opens and displays the font so you can see what the font looks like.
-Click Install Font.
The font is automatically installed in your Library folder so it is available only to you. If you want to make the font available to all users of the computer, drag it to the Computer folder in the Collection column of Font Book.
I don't know why the converted fonts won't open on your Mac. If they are true type fonts (ttf), you don't need to convert them along with open type fonts (otf).http://images.apple.com/pro/pdf/L303878B_Font_TT_v4.pdf
Mac OS X font utilities.http://www.pure-mac.com/font.html#fontfinagler