There isn't any difference between installing this plugin for the first time and upgrading the plugin.

• Download the latest featured release from the Downloads tab
• Save that file as mbla.php in your plugin-directory (usually /wp-content/plugins)
• Activate the plugin called MBLA from the Wordpress plugins adminitration interface

• Reconfigure the options to match your needs

• Remember to add some HTML code on MBLA's HTML option page

• If you want avatars on your posts/pages as well, then you need to add the following line to wherever you want the avatar to show up:

<?php if(function_exists('MyAvatarsNew')) MyAvatarsNew(); ?>

If at any point something is messed up, then just click the "Reset to default values" from the Option page.