To add any of the Font Awesome collection icons, go to https://fontawesome.com/v4.7.0/icons/
Choose the desired icon and click on it.
When opening the selected icons page, highlight the name of the icon (in this case “fa-address-card”) and copy it (right mouse click and copy or key combination ctrl-C).
Then open the section, where you want to place the icon and paste its name in the desired field.
(Right mouse click and paste or key combination ctrl-v).
When the changes have been made, click save changes.
The icon has been added!