Fontawesome is popular icon framework and afterward it becomes default icon on Opencart v2.0 later. It's free for everyone to use. Few years ago, website designers had to draw private icons in difficulties. Fontawesome provides many optional icons and quickly increase amount of icons through new versions. Use steps might feel newly for newbie but you will feel so easy with HTML knowledge.

Specific example, module Video Product Tab of OpencartPlus, some modules allow you to change name for your own language. From this, you can insert fontawesome icon easily with step by step.

Some OpenCart modules has instruction for you to learn how to setup it but not all.

Default name is Video and from here you have a idea to change a fontawesome icon.
 

http://www.opencartexts.com/smarttools/fontawesome is a tool for help you fast to get icon of Fontawesome you might need to use. Select one icon your own idea and copy it to clipboard.
 

Paste and type the name next to it with a blank space to avoid sticking together.

 

Now you can have cloud icon as the picture.