The shortcode used for this section where you can see there has two parameters title and icon so if you want to change the icons you just need to add the name of the icon for eg: icon=”book”
you can take all the icon names from here: Icon Names
Yes you have to use the icons from font awesome but if you want use your icons/images then we need to do minor customization on theme for this mail us to support@flythemes.net and send your site url and the login details.