XF 1.4 add CSS on footer (button + href + text)

[Betclever]

Hello,

Is it possible to add CSS like a button "donate" on the footer with a small description + href?

Please find a print screen of what I want:

I have the code for the button but it is a class so how can I add this?

I'm using a theme from ******* and under the template footer, I can put "html" and this is what I have by example:

<h3>CONTACT US</h3>
<ul>
<li><i class="fa fa-envelope-o"></i> </li>
</ul>

Thanks for your help.