Delete all yst_prominent_words terms

gistfile1.txt

function delete_all_terms(){
	$taxonomy_name = 'yst_prominent_words';
	$terms = get_terms( array(
		'taxonomy' => $taxonomy_name,
		'hide_empty' => false
	) );
	foreach ( $terms as $term ) {
               wp_delete_term($term->term_id, $taxonomy_name); 
	    }		 
}
add_action( 'wp_head', 'delete_all_terms' );

hi where to add this code?

If you know what you are doing, you can add it to your functions.php file. If you want a safer approach, here's how to safely add code snippets in WordPress.