All files has been compressed to minimize the file size so your download is faster.

1. After downloading the file, you need to unstuff it. (I think this is the right Mac term). If you need a tool to unstuff the file, visit Aladdin.
   
2. Unstuff the file.
   
3. Drag and drop folder onto the System folder.  You'll be informed it
   should be saved into the fonts folder.  Press the "return" key.
   
4. Restart to use the new font.
   
   Some helpful articles can also be found at Mac's website.