Alter the Single Post Heading Tag

/**
 * Alter the single post heading tag from H2 to H1
 */
function myprefix_single_post_heading( ) {

	return 'h1';

}
add_filter( 'ocean_single_post_heading', 'myprefix_single_post_heading' );

All PHP snippets should be added via a child theme's functions.php file.