i don''t know which tutorial it is, but anyways..

if it is a font created from a font data. then it probably uses the function CreateFont(...), so check out msdn


HFONT CreateFont(
int nHeight, // height of font
int nWidth, // average character width
int nEscapement, // angle of escapement
int nOrientation, // base-line orientation angle
int fnWeight, // font weight
DWORD fdwItalic, // italic attribute option
DWORD fdwUnderline, // underline attribute option
DWORD fdwStrikeOut, // strikeout attribute option
DWORD fdwCharSet, // character set identifier
DWORD fdwOutputPrecision, // output precision
DWORD fdwClipPrecision, // clipping precision
DWORD fdwQuality, // output quality
DWORD fdwPitchAndFamily, // pitch and family
LPCTSTR lpszFace // typeface name
);


and change the height of your font. if it is a tutorial, i guess there should be a variable to set the height of the font.

if you create your font from a texture file, then depending on how you seperate each letters... change the values in your drawing a)loops or b)values for vertices and tex coords.