Go to Wordpress admin area and click "Plugins" and then "Add New" menu item.
In the right panel (left top) you will see "Upload Plugin" button. Click the button.
Next click the "Choose file" button in right panel (center).
Select zip file of the "WP Live CSS Editor" plugin located on your hard drive and press "Open".
Click "Install Now" and the zip file will upload to your site.
Now click "Activate" button to activate the "WP Live CSS Editor" plugin.
We've tested following plugins published by: Sergio Daroca Fernández with a lot of help from pingram3541 and based on guybedford's drupal plugin http://drupal.org/project/live_css