The plugin provides a widget for receiving virtual currency donations from members of superfluid.
Search for superfluid in the plugins directory and install the plugin by clicking the "install now" link.
Simply place the plugin in your plugins directory and activate it in the "Plugins" section of the WordPress administration interface.
After you have activated the plugin, add the widget and configure it. You must at least enter your superfluid id that you can find at http://thesuperfluid.com/my/account.