Hey Adam,
Adding it is extremely simple and I assume you have basic html knowledge
Edit the file /templates/wanderers/index.php and locate the codes below,
<div class="brands pull-left">
<?php if ($this->params->get('show_heading_title', true)) { ?>
<h1><?php echo JText::_($this->params->get('title', 'Wanderers'));?></h1>
<?php } ?>
<?php if ($this->params->get('show_heading_description', true)) { ?>
<small class="visible-lg">
<?php echo JText::_($this->params->get('description', 'Social template for Joomla'));?>
</small>
<?php } ?>
</div>
Then, change it to,
<div class="brands pull-left">
<img src="http://yoursite.com/images/logo.png" />
</div>