Your question is about the Toolkit. You can manage your training data and classifiers by using the IBM Watson™ Natural Language Classifier Toolkit web application. The toolkit gives you a unified view of all the classifiers that are running in the same Bluemix service instance. So you need to create another classifier and use the toolkit to manage.
I think you can view this document, about Natural Language Classifier using Toolkit.
Obs.: The first classifier is free, but each other you will need to pay.
See the API Reference to use NLC.