This is not theme specific, but for the sake of argument lets say we are talking about the Genesis theme because my query is about child themes.
Lets say I have written a custom CSS class by the name "headline-wrap" and want to wrap my h2 headlines (post titles) with this new class. Since I want this to be strictly a child theme, I don't want to edit the template structure file manually. Maybe its something I have to add in the functions.php
Can someone assist me with this?