Disable Editor in the Global Config and then try add this code
<div class="addthis_toolbox">
<a class="addthis_button_facebook_follow at300b" href="http://www.facebook.com/joomlart" target="_blank" title="Follow on Facebook"><i class="fa fa-facebook"></i></a>
<a class="addthis_button_twitter_follow at300b" href="//twitter.com/joomlart" target="_blank" title="Follow on Twitter"><i class="fa fa-twitter"></i></a>
<a class="addthis_button_google_follow at300b" title="Follow on Google" href="https://plus.google.com/+joomlart" target="_blank"><i class="fa fa-google-plus"></i></a>
<div class="atclear"></div></div>