Question:
How can I install a font from my Delphi application?
Answer:
Just copy a file into Windows\Fonts directory (see SHGetSpecialFolderLocation for CSIDL_FONTS)
As an alternative see the AddFontResource function:
// Adding the font ..
AddFontResource(PChar('XXXFont.TTF'));
SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);
// .. removing the font
RemoveFontResource(PChar('XXXFont.TTF'));
SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);