ff = FontFamily.forName("BBMillbankTall");
font = ff.getFont(FontFamily.SCALABLE_FONT, 12).derive(Font.BOLD);
this would set the font in your application to BBMillbankTall, 12, bold.
You can also set the font for single elements like fields etc.
Cosider it well to use a fixed layout though as different devices have different screen sizes and a solution that fits one may look horrible on another. You can maybe integrate an option screen that allows to set the used font internally.