Check out example codes for "submenu icon font awesome". It will help you in understanding the concepts better.

Code Example 1

<div class="list-group">
  <a class="list-group-item" href="#"><i class="fa fa-home fa-fw" aria-hidden="true"></i>  Home</a>
  <a class="list-group-item" href="#"><i class="fa fa-book fa-fw" aria-hidden="true"></i>  Library</a>
  <a class="list-group-item" href="#"><i class="fa fa-pencil fa-fw" aria-hidden="true"></i>  Applications</a>
  <a class="list-group-item" href="#"><i class="fa fa-cog fa-fw" aria-hidden="true"></i>  Settings</a>
</div>

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