Thank you for the interest in the NodeXL project.
NodeXL can cluster a graph by vertex attribute, by connected component, or via three different algorithmic clustering methods.
Did you select one of these methods from the Group menu and get an error?
Did groups get created in the "Groups" worksheet? Are there entires in the related "Group Vertices" worksheet?
To display groups in the graph the way you would like set the options in the Groups Options (found at the bottom of the Groups menu in the NodeXL ribbon).
Group layouts can also be configured in the Layout Options menu item in the Layout menu in the NodeXL graph pane.