Adding second line to the tag line

@Olivia: There is no such code. As WordPress only have option to add in Site Title and Tagline. If you want second text below tagline, then you need to build child theme and add in manually.

So, first build child theme. You can ready about child theme and download sample child theme from http://catchthemes.com/blog/create-child-theme-wordpress/ and then add the following code in your child theme functions.php file. In the following code, you just need to replace the text Second line text below tagline with your own text.

/**
 * Site Logo, Title, Tagline and Second Tagline
 *
 */
function catchresponsive_site_branding() {
	$options 			= catchresponsive_get_theme_options();

	//Checking Logo
	if ( '' != $options['logo'] && !$options['logo_disable'] ) {
		$catchresponsive_site_logo = '
		<div id="site-logo">
			<a href="' . esc_url( home_url( '/' ) ) . '" title="' . esc_attr( get_bloginfo( 'name', 'display' ) ) . '" rel="home">
				<img src="' . esc_url( $options['logo'] ) . '" alt="' . esc_attr(  $options['logo_alt_text'] ). '">
			</a>
		</div><!-- #site-logo -->';
	}
	else {
		$catchresponsive_site_logo = '';
	}

	if ( display_header_text() ){
		// Show header text if display_header_text is checked
		$catchresponsive_header_text = '
		<div id="site-header">
			<h1 class="site-title"><a href="' . esc_url( home_url( '/' ) ) . '">' . get_bloginfo( 'name' ) . '</a></h1>
			<h2 class="site-description">' . get_bloginfo( 'description' ) . '</h2>
			<h2 class="site-description">Second line text below tagline</h2>
		</div><!-- #site-header -->';
	}
	else {
		$catchresponsive_header_text = '';
	}
	
	if ( '' != $options['logo'] && !$options['logo_disable'] ) {
		if( ! $options['move_title_tagline'] ) {
			$catchresponsive_site_branding  = '<div id="site-branding" class="logo-left">';
			$catchresponsive_site_branding .= $catchresponsive_site_logo;
			$catchresponsive_site_branding .= $catchresponsive_header_text;
		}
		else {
			$catchresponsive_site_branding  = '<div id="site-branding" class="logo-right">';
			$catchresponsive_site_branding .= $catchresponsive_header_text;
			$catchresponsive_site_branding .= $catchresponsive_site_logo;
		}
		
	}
	else {
		$catchresponsive_site_branding	= '<div id="site-branding">';
		$catchresponsive_site_branding	.= $catchresponsive_header_text;
	}
	
	$catchresponsive_site_branding 	.= '</div><!-- #site-branding-->';
	
	echo $catchresponsive_site_branding ;	
}