Hi,
To use the Module, you need to create one instance and then use it.
For the parameters in a Module to be learnt, you just need to pass them to your optimizer:
your_model = Model()
your_loss = center_loss()
your_optimizer = optim.SGD(your_model.parameters() + your_loss.parameters, ...)

# In your training:
features = your_model(inputs)
loss = your_loss(features, labels)
your_optimizer.zero_grad()
loss.backward()
your_optimizer.step()