Hi @vad congrats on starting the course! I’m near the end of my part 1 journey.
If you’ve finished lesson 1, and assuming you’re using the vgg16.py file provided, take some time to review it. Your answer is in there
Also, regarding the format, you basically have to create an output csv file to be similar to the sample submission file that kaggle provides (many ways to do this). You can also take a glance at the next lesson (dogs_cats_redux.ipynb) but try to figure it out yourself first and then look.
for those who will come here for answers, I recommend to check out keras.predict_generator https://keras.io/models/sequential/. Also, the dogs_cats_redux notebook is basically the answer.