First thing to do is to make sure your font is PUA coded. Not all fonts are. Especially some of the older beauties. To learn more about PUA, read this article: WHAT ARE PUA FONTS.

Once you’ve confirmed that, using these fonts is simple if you have version 4.1 Designer Edition or above.

Select your font and type.

Next, highlight the letter you want to change and click on the fancy looking “A” on the text panel. Select the alternate you want. It’s just that easy!