Hi,
First: you've to prepare font to be "Web friendly" - it's should be in all formats like: .eot, .svg, .woff
So go to:
http://www.fontsquirrel.com and create those formats! using online tool.
Second: Copy all unpacked files here: gk_finance_business/fonts/BebasNeue if you wont be using this "old" font, and rename your new filenames to old one. (!) Don't change .css file it should be original old !
So CMS will use "new" font for elements which has be used "old" font,
I know that old name in back-end stay, but who cares
But if you want to add extra font it will be a little more job to do.