To change the title text to say what you want, open the includes/languages/english/meta_tags.php file in your text editor. Find the following line of code:
// page title
define('TITLE', 'Zen Cart!');
// Site Tagline
define('SITE_TAGLINE', 'The Art of E-commerce');
Replace the title and tagline text with your own text, making sure that the single quote marks are not left out and new quote marks are not added.
Save the edited file to includes/languages/english/custom/meta_tags.php and upload it to your server.