According to one source, this is how I use Fontello fonts:
Now it's trivial to make a custom icon webfont, exactly for your needs. First, select the icons you like. Then update glyph codes (optional), and download your webfont bundle. Fontello generates everything you need and then you upload the bundle via this module's configuration page! It's that easy!
Okay. Now what? How do I invoke one of their icons on my webpage?