How to add extra custom social icons to page with same style?

Theres a hacky javascript way I’ve used before which is to use appendChild() to add a Font Awesome icon to the parent node. There will be a container for the icons, find its ID or class and save to a variable, add your icon html (or img tag) to a variable also, then use parent.appendChild(variableNameOfIcon); to add a new icon to the end of the list of children within that node.

You can also adjust the PHP template, either through use of child theme or there may also be a filter hook available depending on the theme to add new icons via filters.