In Windows, you right-click on the font and choose "Install". In KDE, you right-click on the font, go into the "Actions" sub-menu and choose "Install...". Gnom

In Windows, you right-click on the font and choose "Install". In KDE, you right-click on the font, go into the "Actions" sub-menu and choose "Install...". Gnome may be similar, but I'm not sure. In most Linuxes, you can copy the fonts to "/usr/share/fonts/truetype" (as a GUI-independent install mechanism). I don't have a Mac available to test, but I'd bet that there's a font-installation capability either by right-clicking on the font, or in whichever viewer opens when you double-click on it.