How do you change the font in your PSP slim 3.90 m33-3?

Whenever I change the theme of my PSP, the background color and icons change, but not the font. The default font remains even though the screenshots for the themes I've downloaded on the internet are different. Does anybody know how to fix this? Thanks so much! :)How do you change the font in your PSP slim 3.90 m33-3?
I don't know how to but try to download this font and maybe it has instructions on how you can install it.

http://dl.qj.net/New-Cartoon-Fonts-Packa



http://dl.qj.net/index.php?pg=19%26amp;src=fon