1. Use setOutputs() to set the output labels: 

compGraphBuilder.setOutputs("predictSequence");

2. Construct an output layer using the addLayer() method and RnnOutputLayer:

compGraphBuilder.addLayer("predictSequence", new RnnOutputLayer.Builder(LossFunctions.LossFunction.MCXENT)
 .activation(Activation.SOFTMAX).nIn(10).nOut(numOfClasses).build(), "L1");