I have GIMP, and I want to add the font "Holly typed 2 much" onto GIMP, but I don't know how! Please help!

http://www.gimp.org/unix/fonts.html

you don't "put the fonts on the program GIMP", you install the fonts on Windows : http://www.dafont.com/faq.php#win then you use them in Gimp

I installed it onto Windows, but it isn't showing up in GIMP.

Can you see this font with other softwares you've installed ?