First off, most themese are available for automatic install via the "Plugins" link inside WordPress. If the theme you have in mind is not on the official WP site, if you know how to log into your website's control panel, then you can do this very easily yourself. Unzip the theme if it's in a zip file, then log into your control panel and upload the theme files to the folder wp-content/themes/ Once you've done that, just log into WordPress, click on Appearance, and the theme should be showing on the page that comes up. Click it to preview and activate. Adding a logo depends on where you want it, but generally if it goes at the top of the page you just need to click on Appearance, then Theme Editor, and add the logo's location to the file header.php Frank