You can add rounded social share buttons to the sidebar via a widget.
Go to Appearance > Customize > Widgets. And add a 'Custom HTML' widget to the 'Sidebar' widget area. And enter the following HTML, replacing the # with the link to your own social profile.
<ul class="social-icons">
<li>
<a href="#"><i class="fa fa-facebook"></i></a>
</li>
<li>
<a href="#"><i class="fa fa-twitter"></i></a>
</li>
<li>
<a href="#"><i class="fa fa-instagram"></i></a>
</li>
<li>
<a href="#"><i class="fa fa-youtube"></i></a>
</li>
<li>
<a href="#"><i class="fa fa-snapchat"></i></a>
</li>
</ul>