I downloaded the font Chocolate Box to my MAC. Everything went well and I added to my font library. When I used the font the letters are cut off at the top.

That is because the ascender is set too low. It is at 583 and should be at least 853 (the Windows Ascender). You need a font editor to correct this. If you use the lower case only tou won't have this problem.

Or you could spend $10 on the commercial version – which has this corrected, AND a much larger glyph selection:
http://www.cheapprofonts.com/Chocolate_Box_Pro.php