Weka - Clustering - Learning? • /r/MachineLearning

Hey guys I got a few questions on WEKA, I know know it's not a favored program here but I'm kind of stuck and I'd appreciate any help whatsoever. Basically I'm new to ML which is why I'm using WEKA to get a grasp on algorithms, clustering, and all that stuff everything before transitioning to something python based. My question relates to clustering and how the algorithms actually "learn" my understanding is that with clustering I should be able to feed the program some unlabeled data and it will do it's best to cluster the data into an unknown amount of clusters or a user defined amount. Once a model is built I should be able to re-run the clustering algorithm again to build upon this and hopefully get a more precise image of each cluster the second time round, repetition should hopefully build a model which can correctly identify which cluster new data belongs to if it's introduced. Is this the correct way of thinking, if it is how can I do this in WEKA?