If you want to see to what cluster each row in the training data belongs:
1. enable drillthrough on the model
2. reprocess the model
3. open model viewer, right click on a cluster and select "Drill Through" to see rows that belong to the cluster.
If you want to assign rows to clusters where rows are not in the training data, then you need to execute query to predict what cluster the row belongs to. Look here to get help with the query http://msdn.microsoft.com/en-us/library/cc280440.aspx