This is how you use the TensorBoard callback:
from keras.callbacks import TensorBoard
tensorboard = TensorBoard(log_dir='./logs', histogram_freq=0,
write_graph=True, write_images=False)
# define model
model.fit(X_train, Y_train,
batch_size=batch_size,
epochs=nb_epoch,
validation_data=(X_test, Y_test),
shuffle=True,
callbacks=[tensorboard])