Changing an icon image is very easy. Visit https://fontawesome.com/v4.7.0/icons/ to view a library of available icons and simply just change the name on the dashboard.
In the example below, we will change the at sign in the 'What We Do Section" of the HTML editor dashboard by changing 'fa-at' to the new icon name of 'archive' - So new code would read 'fa-archive' and the webpage will now display the archive icon image.
There are hundreds to choose from so have some fun!
