BooleanOperation.xml (3.1 KB) is an XML plugin you can load from the Tools -> Manage Plugins… menu item. In the plugin manager dialog, click “Load New…” and navigate to where you saved this XML plugin. Click OK. After you have loaded it, you will have a Boolean Operation filter available in the Filters menu. Click on a polydata source and apply this filter. In the dialog that appears, you can pick a second polydata source.