Basic Use
Font Awesome Icons are designed to be used with HTML inline elements like <i> and <span> as shown below.
However, the preferred HTML element for Font Awesome Icons is <i> and <span> for its styling, both the elements work but we suggest using the element <i> for these icons.
Each icon is defined using two classes, one of them is required for all icons and the other varies with each icon that refers icon name.
- Class 
fais required for each icon - Class 
fa-namedetermines the icon name, where the wordnamemust be replaced with the actual icon name 
<i class="fa fa-cubes"></i>
<span class="fa fa-users"></span>
Reference
Here is the official documentation for Font Awesome, which can be referred to for icons availability.
Examples
<!DOCTYPE html>
<html>
<head>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
</head>
<body>
    <i class="fa fa-cubes"></i>
    <span class="fa fa-users"></span>
</body>
</html>
Overall
It's quite easy to include and use Font Awesome Icons in our web applications.
Related Links
- Font Awesome V4 - Tutorial
 - Font Awesome V4 - Introduction
 - Font Awesome V4 - Icon Sizes
 - Font Awesome V4 - Icon Styles
 - Font Awesome V4 - Fixed Width Icons
 - Font Awesome V4 - Icons as List bullets
 - Font Awesome V4 - Bordered Icons
 - Font Awesome V4 - Pulled Icons
 - Font Awesome V4 - Animated Icons
 - Font Awesome V4 - Rotated Icons
 - Font Awesome V4 - Flipped Icons
 - Font Awesome V4 - Stacked Icons