Make sure you copy that in your Child theme’s root folder, then edit it.

You would start by replacing the logo image code in that new header.php:

<?php	if($logo) { ?>
							<div class='logo_img <?php echo $logo_transparent ? "transparent_logo_".esc_attr($transparent_logo_effect) : "";?>'>
								<a href="<?php echo esc_url(home_url('/')); ?>" title="<?php echo esc_attr(get_bloginfo('name', 'display')); ?>" rel="home">
									<img src="<?php echo esc_url($logo); ?>" alt="<?php bloginfo('name'); ?>"/>
									<?php if($logo_transparent) { ?>
										<span id="transparent_logo"><img src="<?php echo esc_url($logo_transparent); ?>" alt="<?php bloginfo('name'); ?>"/></span>
									<?php } ?>
								</a>
							</div>
				<?php	} else { ?>
							<div class='logo_img <?php echo $logo_transparent ? "transparent_logo_".esc_attr($transparent_logo_effect) : "";?>'>
								<a href="<?php echo esc_url(home_url('/')); ?>" title="<?php echo esc_attr(get_bloginfo('name', 'display')); ?>" rel="home">
									<img src="<?php echo esc_url(get_template_directory_uri().'/images/logo.png'); ?>" alt="<?php bloginfo('name'); ?>"/>
									<?php if($logo_transparent) { ?>
										<span id="transparent_logo"><img src="<?php echo esc_url(get_template_directory_uri().'/img/logo.png'); ?>" alt="<?php bloginfo('name'); ?>"/></span>
									<?php } ?>
								</a>
							</div>
				<?php	} ?>

and replace it with your TEXT logo, for example:

<h2> My Logo </h2>

Then you would style your logo with simple CSS like so:

#logo h2 {
font-size: 36px;
color: red;
}

etc.

Let me know if I can further help you with the CSS once you have the text on there!
URL will be helpful too!