Problems inserting html

I am trying to insert font icons following this example.

I added the necessary lines of code to my html and css but the icons are not showing up when I insert the HTML on my page.

Using the HTML icon to insert html into the text editor, this is what I entered.

But nothing happens after I press OK. When I view the html of the published site, this is the only code that shows up where I entered the above code.

 

My site is the old version before the layout was changed.