To make the display block when clicking this icon:
<div class="index-navi-frame-box">
<p onclick="expandFunction()">
<i class="fa fa-bars"></i>
</p>
</div>
Here is what it should change to:
<div class="index-navi-expanded"></div>
CSS for index-navi-expanded:
.index-navi-expanded{
width: 100%;
height: 30%;
background-color: #757575;
position: relative;
display: none;
}