Hi, i would add another social icon.
I have modified these files:

I added the new code for the icon youtube in template.css
#jf-social li a.button-youtube {
background-image: url(../images/youtube.png);
}

Also I added the code in index.php
<?php if ($templateparams->get('youtubeicon') && $templateparams->get('youtubelink') != '') : ?>
<li><a class="button-youtube" href="<?php echo $templateparams->get('youtubelink'); ?>" target="_blank"></a></li>
<?php endif; ?>

and also the code in templateDetails.xml
<field name="youtubeicon" type="radio" default="1"
label="Show Youtube Icon"
description="Select an option">
<option value="0">No</option>
<option value="1">Yes</option>
</field>

<field name="youtubelink" type="text" default="#"
label="Youtube Link"
description="Please add your youtube link here"
filter="string" />

but the icon does not appear.
What other files I have to change?

add to css approximately 249 line code:

example:

#jf-social li a.button-youtube {
background-image: url(../images/youtube.jpg);
}

Perhaps you have not read, but it is the first thing I did ...