You should be able to choose Text / Font / Edit Font list to display the Edit Font List dialog box. The top listbox shows your current available fonts, and should by default have "Add fonts below" selected.
Below that, you have a list of fonts installed on your computer in the right hand list box, and an empty list box on the left.
Select the font you want from the right list box (in this case, myriad pro), and use the buttons to move it to the lefthand box. Select alternates to Myriad for those people that might not have it installed the same way.
When you're happy, click OK. Now, the new font choice will show up as an option in the properties box, or if you choose Text/Fonts.
Yes but I want to add Myriad Pro so it is an option in the Macromedia font list. I suspect I will need to add it to the "Macromedia" directory after downloading the font from the Internet or obtaining it somewhere