Okay it’s hard to say without seeing the code, but I would first make sure the font has been declared in the child theme’s style.css file.
Then, double check that your markup matches their example:
<a href="https://twitter.com/qimzu"><span class="socicon">a</span> @qimzu</a>
Currently, the social-icons.php has PHP that gets the user input and dynamically adds the icons, but you can hard-code in the values making things much simpler. The social-icons.php file in your child theme could simply look something like this:
<ul class="social-media-icons">
<li><a href="https://twitter.com/qimzu"><span class="socicon">a</span> @qimzu</a></li>
<li><a href="https://twitter.com/qimzu"><span class="socicon">a</span> @qimzu</a></li>
<li><a href="https://twitter.com/qimzu"><span class="socicon">a</span> @qimzu</a></li>
</ul>
Using the child theme is a bit more work, but it will future-proof your changes. Otherwise, when you update Tracks will overwrite the changes you’ve made to it.