Damned is a great font style that allows you to quickly give a grunge, eroded, scary look to any text string.
To install the Damned font simply unzip the archive and put the font file (.ttf, .otf) into /Library/Fonts . Damned font integrates quickly into your system and you can easily access the custom glyphs though any text editing application.
Mac OS X comes with pre installed font styles and Damned will simply be added to your pre existent library. The process is managed through the Font Book application, where you can easily browse and preview your currently installed fonts.
To learn more about dealing with the Font Book application you can easily access the Apple support page HERE.
NOTE: Damned font is free for personal use only.