Every text font should be directly installed in the running system, as you normally do it for other external applications.
As long as the cardPresso software is executed any time after a new font is installed, it should have immediate access to the same.
If you require to apply multiple variants of the same font, you’ll have to use TrueType (.ttf) installers for each one of them, in order to ensure that they’ll all be listed separately in the cardPresso Font Family option.