Instalation is easy, just install the plugin. It automatically creates a custom post type googlemaps wich can be used. If you use this it will automatically creates an archive page with the items on it.
If you want to use googlemaps with an other post type, you can change the main post type of the googlemaps. To support other types you also have to check the support types on that post type, this will create the meta box on the admin page.