If you were using {{ site.fontawesome.name }} {{ site.fontawesome.minor_version }}, you should be able to just switch to {{ site.forkawesome.name }} {{ site.forkawesome.minor_version }} and get all the benefits from it. If you were using npm or composer packages, replace the ones you were using by this {{ site.forkawesome.name }} ones. Or if you downloaded a static copy of {{ site.fontawesome.name }}, download the latest version of {{ site.forkawesome.name }} and replace CSS and font files in your project and you should be good to go.
We paid special attention not to change unicode codepoints for the existing icons, nor changed the CSS class names or icon names from {{ site.fontawesome.name }} {{ site.fontawesome.minor_version }}. Though we added a few more icons and made the process of contributing to this project much easier. Though, if you see a mistake, please don't hesitate to file a bug.