Upload the folder containing mp2wp.php to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.
To add a Metaplace world on a sidebar, browse to Design > Widgets and add the 'mp2wp widget" to desired sidebar. Configure the world title, embedding dimensions and world name and save your changes.
To add a Metaplace world to any blog-post or page just add the markup [mp2wp]worldname,width,height[/mp2wp], for example [mp2wp]ComicEmporium,400,350[/mp2wp].