How to Hide the "Floating Share Button" Admin Menu

function plt_hide_flexishare_pro_menus() {
	//Hide the "Settings → Floating Share Button" menu.
	remove_submenu_page('options-general.php', 'flexishare-settings');
}

add_action('admin_menu', 'plt_hide_flexishare_pro_menus', 11);

Where do I put this code?