QUESTION How to add my company logo?

[datiswous]

First upload your logo into your website files and copy the full picture url.
Go into your admin panel, on Theme / Modify your theme and edit the "header.inc.php" file.

Replace :
    <?php get_site_name(); ?>

by :
    <img src="http://www.your.full.path.to.company.logo.png" alt="Your Company Name" />

Or something like:

PHP Code:

<a href="<?php get_site_url(); ?>"><img src="<?php get_theme_url(); ?>/images/logo.jpg" alt="<?php get_site_name(); ?>"></a> 


This code is making the logo also a link to the homepage. 

<?php get_site_url(); ?> is changed to the domain url when rendering the page.
<?php get_theme_url(); ?> is changed to the rootfolder of the theme.
<?php get_site_name(); ?> is changed to the name of the site as specified in Website Settings in GS.

For more info on template tags see here: http://get-simple.info/wiki/themes:template_tags

There are actually plugins which make it possible to implement a configuration page for a theme so you can change such settings. But theme makers do not often implement them.

Theme Settings
GS Custom Settings