The beauty behind using icon fonts is that once you've imported them into your site, you can change their size, colour or other properties as you would any other font. So for example:
HTML
<i class="fa fa-bullhorn"> </i> hello world
CSS
i.fa{
font-size:100px;
color:olive;
}
Hope this helps!
See this live: http://jsfiddle.net/panchroma/GLVSx/